EuroClonality/BIOMED-2 guidelines for interpretation and reporting of Ig/TCR clonality testing in suspected lymphoproliferations

Comparison of 2 T-Cell Receptor-γ Clonality Assays on Skin Biopsies Suspicious for Mycosis Fungoides

ABSTRACT

PCR-based fragment analysis of the T-cell receptor (TCR) gene is used extensively in diagnostic labs to assess clonality in T-cell populations in multiple tissue sites. Of the numerous TCR assays that have been reported, studies assessing use on biopsies suspicious for mycosis fungoides specifically are lacking. We compared clonality findings from a previously run 2-tube/2-fluorochrome dye assay to a redesigned 1-tube/1-fluorochrome dye assay on formalin-fixed skin biopsies. Overall, the accuracy of the 2-tube assay was marginally better (75.7% vs. 71.4%), when using clinical history combined with histologic diagnosis as the gold standard. The 2-tube assay had better sensitivity (73.7% vs. 65.8%), while the 1-tube assay had superior specificity (93.8% vs. 87.5%). Clonality results were easier to interpret with the 1-tube assay. In nearly 19% of cases, a change of assays on the same biopsy resulted in a change of clonality interpretation. For laboratories that change TCR-γ clonality assays, follow-up biopsies for mycosis fungoides assessment may result in a change of diagnosis.

T-Cell-Rich Hodgkin Lymphoma With Features of Classic Hodgkin Lymphoma and Nodular Lymphocyte-Predominant Hodgkin Lymphoma: A Borderline Category With Overlapping Morphologic and Immunophenotypic Features

CONTEXT.—

It is known that a subset of cases of classic Hodgkin lymphoma (CHL) with B-cell-rich nodules (lymphocyte-rich CHL) exhibits morphologic and immunophenotypic features that overlap with nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL), raising diagnostic difficulties that can be resolved in most cases by performing an adequate battery of immunohistochemical studies.

OBJECTIVE.—

To fully characterize cases of T-cell-rich Hodgkin lymphoma where a specific diagnosis of NLPHL (ie, pattern D) or CHL could not be made even after complete immunophenotypic investigation.

DESIGN.—

The clinical, immunomorphologic, and molecular (when applicable) presentation of 3 cases of T-cell-rich Hodgkin lymphoma was thoroughly investigated.

RESULTS.—

These 3 cases harbored lymphocyte-predominant-like and Hodgkin and Reed-Sternberg-like cells that partially expressed B-cell and CHL markers and were negative for Tiftein-Barr virus-encoded small RNA, in a T-cell-rich background with residual follicular dendritic cell meshworks; 1 case had frequent and the other 2 cases scant/absent eosinophils and plasma cells. Two patients with advanced-stage (III or IV) disease presented with axillary and supraclavicular lymphadenopathy, respectively, and without B symptoms. These patients underwent NLPHL-like therapeutic management with 6 cycles of R-CHOP (rituximab, cyclophosphamide, doxorubicin hydrochloride [hydroxydaunorubicin], vincristine sulfate [Oncovin], and prednisone) chemotherapy; both are in complete remission 7 years posttherapy. One patient presented with stage I disease involving an internal mammary lymph node without B-symptoms and was treated with surgical excision alone; this patient is also in complete remission 1 year later.

CONCLUSIONS.—

These cases illustrate overlapping features of T-cell-rich NLPHL and CHL with neoplastic cells expressing both B-cell program and CHL markers. This underrecognized overlap has not been fully illustrated in the literature, although it portrays a therapeutic challenge. These neoplasms may deserve in-depth investigation in the future that may bring up diagnostic or theragnostic implications.

Evaluation of next-generation sequencing for measurable residual disease monitoring in three major fusion transcript subtypes of B-precursor acute lymphoblastic leukaemia

The use of next-generation sequencing (NGS) for monitoring measurable residual disease (MRD) in acute lymphoblastic leukaemia (ALL) has been gaining traction. This study aimed to investigate the utility of NGS in MRD monitoring for the three major fusion transcript (FT) subtypes of B-precursor ALL (B-ALL). The MRD results for 104 bone marrow samples from 56 patients were analysed through NGS and real time quantitative reverse transcription PCR (RT-qPCR) for the three major FTs: BCR::ABL1, TCF3::PBX1, and ETV6::RUNX1. To validate the NGS approach, NGS-MRD was initially compared with allele-specific oligonucleotide-qPCR-MRD, and the coefficient of determination was good (R2=0.8158). A subsequent comparison of NGS-MRD with FT-MRD yielded a good coefficient of determination (R2=0.7690), but the coefficient varied by subtype. Specifically, the R2 was excellent for TCF3::PBX1 ALL (R2=0.9157), good for ETV6::RUNX1 ALL (R2=0.8606), and subpar for BCR::ABL1 ALL (R2=0.5763). The overall concordance between the two methods was 83.7%, and an excellent concordance rate of 95.8% was achieved for TCF3::PBX1 ALL. Major discordance, which was defined as a >1 log difference between discordant NGS-MRD and FT-MRD, occurred in 6.7% of the samples, with all but one sample being BCR::ABL1 ALL. Among the four non-transplanted patients with BCR::ABL1-MRD (+)/NGS-MRD (-), three did not relapse after long-term follow-up. Our finding indicates that NGS-MRD has a better prognostic impact than RT-qPCR-MRD in ETV6::RUNX1 and BCR::ABL1 ALL, whereas in TCF3::PBX1 ALL, both methods exhibit comparable efficacy.

Immunoglobulin light chain transcript detection by ultrasensitive RNA in situ hybridization for B-cell lymphoma diagnosis

Evaluation of B-cell clonality can be challenging in the interpretation of lymphoid infiltrates on tissue sections. Clonality testing based on IG gene rearrangements analysis by PCR (IG-PCR) is the gold standard. Alternatively, B-cell clonality can be assessed by the recognition of immunoglobulin light chain (IgLC) restriction, by immunohistochemistry (IHC), chromogenic in situ hybridization (ISH) or flow cytometry (FC). IG-PCR requires molecular facilities, and FC requires cell suspensions, both not widely available in routine pathology units. This study evaluates the performance of B-cell clonality detection by IgLC-RNAscope® (RNAsc) in a group of 216 formalin-fixed, paraffin-embedded samples including 185 non-Hodgkin B-cell lymphomas, 11 Hodgkin lymphomas (HL) and 20 reactive samples. IgLC-RNAsc, performed in parallel with FC in 53 cases, demonstrated better performances (93% vs 83%), particularly in diffuse large B-cell lymphoma (98% vs 71%) and follicular lymphoma (93% vs 83%) diagnosis. IgLC-RNAsc was also superior to IHC and ISH especially in samples with limited tumor cell content, where IG-PCR was not informative. Performed for the first time on mediastinal lymphomas, IgLC-RNAsc identified monotypic IgLC transcripts in 69% of primary mediastinal large B-cell lymphoma (PMBCL) and 67% of mediastinal gray zone lymphomas (MGZL). IGK/L double-negative cells were detected in 1 PMBCL, 2 MGZL, and all classical HL, while monotypic IgLC expression appeared to be a hallmark in nodular lymphocyte-predominant HL. IgLC-RNAsc demonstrates to be a powerful tool in B-cell lymphoma diagnosis, above all in challenging cases with limited tumor cell content, ensuring in situ investigations on mechanisms of Ig regulation across lymphoma entities.

Primary cutaneous, epidermotropic mycosis fungoides-like presentation: critical appraisal and description of two novel cases, broadening the spectrum of ALK+ T-cell lymphoma

Leading from a two-case series, including two patients receiving a diagnosis of epidermotropic T-cell lymphoma, featuring a mycosis fungoides (MF)-like clinical pattern and ALK expression and molecular alteration, we performed a critical appraisal of ALK+ primary cutaneous T-cell lymphomas (pcTCL). Considering our patients and the literature, 32 cases were retrieved, 7 of which featured an MF-like clinical picture over a 4-to-20-year period. MF-like cases show distinctive histology, comprising a predominantly epidermotropic infiltration of small-to-large, atypical-to-pleomorphic, with few anaplastic cells, negligible-to-intense CD30-expression, and a CD4+/cytotoxic granule+ phenotype. These features should prompt a search for ALK expression captured by the ALK D5F3 clone. Bona fide ALK+ pcTCL is very rare, and existent data suggest the presence of a broader pattern of disease, including instances mimicking MF and/or primary cutaneous CD8+ aggressive epidermotropic cytotoxic T-cell lymphoma. The major challenges in dealing with this subset include prodromal phases, misinterpreted as inflammatory dermatosis or parapsoriasis/early phase MF both clinically and histologically, while recognition of its ALK-driven biology is hampered both by the unusual clinic-pathologic pattern of the disease, which stands apart from the classical (i.e., nodal) picture of ALK+ anaplastic large cell lymphoma and by the low sensitivity of ALK1 clone. Data on its optimal management are far from being conclusive: An MF-like approach is currently chosen, but depending on CD30 and, most notably, ALK expression, a targeted therapy could be envisaged in advanced stages, as clinical response to ALK inhibition was documented in one patient.

Comparative analysis of primer sets for the assessment of clonality in feline lymphomas

Introduction

Lymphomas are among the most important and common malignant tumors in cats. Differentiating lymphomas from reactive lymphoid proliferations can be challenging, so additional tools such as clonality assessment by PCR are important in diagnosis finding. Several PCR assays have been developed to assess clonality in feline lymphomas. For T-cell lymphomas TRG (T-cell receptor gamma) genes are the preferred target whereas for B-cell lymphomas most primer sets target immunoglobulin heavy chain (IGH) genes. Here we compare commonly used diagnostic primer sets for the assessment of clonality in feline lymphomas under controlled conditions (i.e., identical sample set, PCR setup, amplicon detection system).

Methods

Formalin-fixed and paraffin-embedded samples from 31 feline T-cell lymphomas, 29 B-cell lymphomas, and 11 non-neoplastic controls were analyzed by PCR combined with capillary electrophoresis.

Results and discussion

We show that the combination of the primer sets published by Weiss et al. and Mochizuki et al. provided the best results for T-cell clonality, i.e., correctly assigns most populations as clonal or polyclonal. For B-cell clonality, the combination of the primer sets by Mochizuki et al. and Rout et al. gave the best results when omitting the Kde gene rearrangement due to its low specificity. This study rigorously evaluated various primer sets under uniform experimental conditions to improve accuracy of lymphoma diagnostic and provides a recommendation for achieving the highest diagnostic precision in lymphoma clonality analysis.

Tissue-Matched IgH Gene Rearrangement of Circulating Tumor DNA Shows Significant Value in Predicting the Progression of Diffuse Large B Cell Lymphoma

BACKGROUND

Evidence has demonstrated that monitoring of the variable, diversity, and joining gene segments (VDJ) rearrangement of the immunoglobulin (Ig) genes in the circulating tumor DNA (ctDNA) is of value in predicting the outcomes of diffuse large B cell lymphoma (DLBCL). In this study, we investigated the role of VDJ rearrangement proportion in ctDNA for predicting DLBCL progression.

METHODS

Patients diagnosed with newly diagnosed DLBCL were included in this study. The VDJ sequences of IgH were detected using next-generation sequencing (NGS) in formalin-fixed paraffin-embedded tissue and/or peripheral blood. The clonotype of the highest proportion in the peripheral blood was defined as the "dominant circulating clonotype," whilst the clonotype of the highest proportion in matched tissue that is detected in peripheral blood was defined as the "dominant tissue-matched clonotype." The decision tree, a machine learning-based methodology, was used to establish a progression-predicting model through a combination of "dominant tissue-matched clonotype" proportion or "dominant circulating clonotype" proportion, and the clinicopathological information, including age, sex, cell of origin, stage, international prognostic index, lactate dehydrogenase, number of extranodal involvements and β2-microglobulin.

RESULTS

A total of 55 patients with eligible sequencing data were used for prognosis analysis, among which 36 patients had matched tissue samples. The concordance rate of "dominant circulating clonotype" and "dominant tissue-matched clonotype" was 19.44% (7/36). The decision tree model showed that the combination of extranodal involvement event and "dominant circulating clonotype" proportion (≥37%) had a clinical value in predicting the prognosis of DLBCL following combined chemotherapy (sensitivity, 0.63; specificity, 0.81; positive prediction value (PPV), 0.59; negative prediction value, 0.83; kappa value, 0.42). Noticeably, the combination of the "dominant tissue-matched clonotype" and extranodal involvement event showed a higher value in predicting the progression (sensitivity, 0.85; specificity, 0.78; PPV, 0.69; kappa value, 0.64).

CONCLUSION

IgH proportion detected in the ctDNA samples traced from tissue samples has a high clinical value in predicting the progression of DLBCL.

Clinical Use of Molecular Biomarkers in Canine and Feline Oncology: Current and Future

Molecular biomarkers are central to personalised medicine for human cancer patients. It is gaining traction as part of standard veterinary clinical practice for dogs and cats with cancer. Molecular biomarkers can be somatic or germline genomic alterations and can be ascertained from tissues or body fluids using various techniques. This review discusses how these genomic alterations can be determined and the findings used in clinical settings as diagnostic, prognostic, predictive, and screening biomarkers. We showcase the somatic and germline genomic alterations currently available to date for testing dogs and cats in a clinical setting, discussing their utility in each biomarker class. We also look at some emerging molecular biomarkers that are promising for clinical use. Finally, we discuss the hurdles that need to be overcome in going 'bench to bedside', i.e., the translation from discovery of genomic alterations to adoption by veterinary clinicians. As we understand more of the genomics underlying canine and feline tumours, molecular biomarkers will undoubtedly become a mainstay in delivering precision veterinary care to dogs and cats with cancer.

Indolent T-cell Lymphoproliferative Disorder of the Gastrointestinal Tract Mimicking Crohn's Disease

Indolent clonal T-cell lymphoproliferative disorder (iCTLD-GI)/indolent T-cell lymphoma of the gastrointestinal tract (iTLP-GI) poses diagnostic challenges, and despite its rarity, accurate diagnosis is crucial for appropriate management. We report the case of 34-year-old female with a 19-year history of gastrointestinal symptoms suggestive of inflammatory bowel disease (IBD). Subsequent evaluation revealed iCTLD-GI/iTLP-GI with extensive Crohn's disease-like morphological alterations, previously unreported. These macroscopic and microscopic aspects underscore the need for a comprehensive evaluation to avoid misdiagnosis with IBD. Additionally, molecular studies have identified potential therapeutic targets, highlighting the evolving management strategies. This case underscores the diagnostic complexity of iCTLD-GI/iTLP-GI, especially when the condition mimicks IBD such as Crohn's disease.

Diagnostic methods for primary vitreoretinal lymphoma: A systematic review

Primary vitreoretinal lymphoma is a potentially aggressive intraocular malignancy with poor systemic prognosis and sometimes significant diagnostic delays as it may masquerade as chronic uveitis. Despite the variety of diagnostic techniques, it is unclear which modality is most accurate in the diagnosis of PVRL. A systematic literature search was conducted on Ovid MEDLINE, EMBASE and the Cochrane Controlled Register of Trials for studies published between January, 2000, and June, 2023. Randomized controlled trials (RCTs) reporting on the following diagnostic tools used to diagnose patients with PVRL were included: cytology, flow cytometry, MYD88 L265P mutation, CD79B mutation, interleukin 10/interleukin-6 (IL-10/IL-6) ratio, polymerase chain reaction (PCR) for monoclonal immunoglobulin heavy chain (IgH) and immunoglobulin kappa light chain (IgK) rearrangements, and imaging findings. The aggregated sensitivity of each diagnostic modality was reported and compared using the chi-squared (χ2) test. A total of 662 eyes from 29 retrospective studies reporting on patients diagnosed with PVRL were included. An IL-10/IL-6 ratio greater than 1 had the highest sensitivity (89.39%, n = 278/311 eyes, n = 16 studies) for PVRL, where the sensitivity was not significantly different when only vitreous samples were drawn (88.89%, n = 232/261 eyes, n = 13 studies) compared to aqueous samples (83.33%, n = 20/24, n = 2) (p = 0.42). Flow cytometry of vitreous samples gave a positive result in 66/75 eyes (88.00%, n = 6 studies) with PVRL, and monoclonal IgH rearrangements on PCR gave a positive result in 354/416 eyes (85.10%, n = 20 studies) with PVRL. MYD88 L265P and CD79B mutation analysis performed poorly, yielding a positive result in 63/90 eyes (70.00%, n = 8 studies) with PVRL, and 20/57 eyes (35.09%, n = 4 studies) with PVRL, respectively. Overall, our systematic review found that an IL-10/IL-6 ratio greater or equal to one may provide the highest sensitivity in identifying patients with PVRL. Future studies are needed to employ multiple diagnostic tools to aid in the detection of PVRL and to further establish nuanced guidelines when determining the optimal diagnostic tool to use in diverse patient populations.

Profiling of Copy Number Alterations Using Low-Coverage Whole-Genome Sequencing Informs Differential Diagnosis and Prognosis in Primary Cutaneous Follicle Center Lymphoma

Primary cutaneous follicle center lymphoma (PCFCL) has an excellent prognosis using local treatment, whereas nodal follicular lymphoma (nFL), occasionally presenting with cutaneous spread, often requires systemic therapy. Distinction of the 2 diseases based on histopathology alone might be challenging. Copy number alterations (CNAs) have scarcely been explored on a genome-wide scale in PCFCL; however, they might serve as potential biomarkers during differential diagnosis and risk stratification. Low-coverage whole-genome sequencing is a robust, high-throughput method for genome-wide copy number profiling. In this study, we analyzed 28 PCFCL samples from 20 patients and compared the copy number profiles with a cohort of diagnostic samples of 64 nFL patients. Although the copy number profile of PCFCL was similar to that of nFL, PCFCL lacked amplifications of 18q, with the frequency peaking at 18q21.33 in nFL cases involving the BCL2 locus (PCFCL: 5.0% vs nFL: 31.3%, P = .018, Fisher exact test). Development of distant cutaneous spread was significantly associated with higher genomic instability including the proportion of genome altered (0.02 vs 0.13, P = .033) and number of CNAs (2 vs 9 P = .017), as well as the enrichment of 2p22.2-p15 amplification involving REL and XPO1 (6.3% vs 60.0%, P = .005), 3q23-q24 amplification (0.0% vs 50.0%, P = .004), 6q16.1-q23.3 deletion (6.3% vs 50.0%, P = .018), and 9p21.3 deletion covering CDKN2A and CDKN2B loci (0.0% vs 40.0%, P = .014, all Fisher exact test) in PCFCL. Analysis of sequential tumor samples in 2 cases harboring an unfavorable clinical course pointed to the acquisition of 2p amplification in the earliest common progenitor underlining its pivotal role in malignant transformation. By performing genome-wide copy number profiling on the largest patient cohort to date, we identified distinctive CNA alterations conceivably facilitating the differential diagnosis of PCFCL and secondary cutaneous involvement of nFL and potentially aiding the risk stratification of patients with PCFCL in the future.

Molecular B-cell clonality assay in minor salivary glands as a useful tool for the lymphoma risk assessment in Sjögren's syndrome

OBJECTIVES

Non-Hodgkin's lymphoma (NHL) risk assessment is crucial in Sjögren's syndrome (SS). We studied the prevalence of clonal immunoglobulin gene rearrangements in minor salivary glands (MSG) and their correlations with lymphoma occurrence and with previously established NHL predictors.

METHODS

Molecular B-cell expansion was studied in fresh-frozen MSG of 207 patients with either suspected SS or with suspected lymphoma during SS, using a standardised multiplex PCR assay combined with heteroduplex analysis by microcapillary electrophoresis. The assignation of clonal cases was based on EuroClonality consortium guidelines.

RESULTS

Among 207 studied patients, 31 (15%) had MSG monoclonal B-cell infiltration. Monoclonality was significantly more frequent in patients with SS (28/123, 22.8%) compared with patients without SS (3/84, 3.6%, P<0.001). Monoclonal B-cell infiltration in MSG of SS patients correlated significantly with ongoing salivary gland NHL, salivary gland swelling, CD4+ T-cell lymphopenia, rheumatoid factor (RF) activity, low complement levels and type 2 mixed cryoglobulinemia. The accumulation of biological risk factors was associated with a higher rate of MSG B-cell monoclonality given that patients with only positive RF had no probability of MSG B-cell monoclonality, RF-positive patients with 1 or 2 other risk factors had a 25.0% and 85.7% probability of MSG B-cell monoclonality, respectively.

CONCLUSION

The detection of MSG monoclonal B-cell expansion by this easy-to-perform molecular assay is useful, both at the time of diagnosis and during the course of SS. Monoclonal B-cell expansion is associated with a subset of SS patients presenting either ongoing lymphoma or other established lymphoma predictive factors.

Differentiating Between Epstein-Barr Virus-positive Lymphoid Neoplasm Relapse and Post-transplant Lymphoproliferative Disorder After Sex-mismatched Hematopoietic Stem Cell Transplantation

After allogeneic hematopoietic stem cell transplantation (HSCT), accurate differentiation between donor-derived post-transplant lymphoproliferative disorder (PTLD) and relapse of recipient-derived lymphoproliferative disorder (LPD) is crucial for determining treatment. Conventional diagnostic approaches for PTLD include histopathological examination, flow cytometry, and chimerism analysis of bulk tumor tissue. However, these methods are inconclusive in cases in which the primary disease is an Epstein-Barr virus (EBV)-positive LPD and is of the same lineage as that of the post-HSCT LPD tumor cells. Particularly, in cases where the number of tumor cells in the tissue is low, it is difficult to determine the origin of tumor cells. In this study, we developed a new method to simultaneously detect signals using sex chromosome fluorescence in situ hybridization, immunofluorescence staining, and EBV-encoded small RNA in situ hybridization on a single section of formalin-fixed paraffin-embedded histopathological specimen. The utility of the method was validated using specimens from 6 cases of EBV-positive LPD after sex-mismatched HSCT that were previously difficult to diagnose, including Hodgkin lymphoma-like PTLD that developed after HSCT for Hodgkin lymphoma and recurrence of chronic active EBV infection. This method successfully preserved the histologic structure after staining and allowed accurate determination of tumor cell origin and lineage at the single-cell level, providing a definitive diagnosis in all cases. This method provides a powerful tool for the diagnosis of LPDs after sex-mismatched HSCT.

Usefulness and Limitations of Current Diagnostic Strategies for Pulmonary Mucosa-Associated Lymphoid Tissue Lymphoma: Lessons Learned From a Large Cohort

CONTEXT.—

The pathologic diagnosis of pulmonary extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) is challenging.

OBJECTIVE.—

To evaluate the diagnostic usefulness and limitations of current diagnostic strategies for pulmonary MALT lymphoma.

DESIGN.—

A retrospective review of 120 cases of pulmonary MALT lymphoma from 2014 through 2021 was performed.

RESULTS.—

Clinicoradiologic presentations overlapped with previous observations in patients with MALT lymphoma, such as a wide age range, female predominance, frequent association with autoimmune disease or immunodeficiency, and broad imaging findings. The histopathologic diagnosis was based on a combination of morphology, immunohistochemistry, and demonstration of B-cell lineage clonality. Two-thirds (76 of 113) of MALT lymphomas had lymphoplasmacytoid cytomorphology. Occasionally, MALT lymphomas were associated with granulomas/giant cells (29%, 35 of 120) or immunoglobulin deposition disease (21%, 25 of 120), including light chain/heavy chain deposition disease, amyloidosis, and/or crystal storing histiocytosis. While CD5, CD10, Bcl-2, and Bcl-6 rarely revealed aberrancies, aberrant CD43 expression either on B-cells or on plasma cells was detected in 42% (27 of 64) of cases, including cases for which proof of clonality could not be obtained. κ/λ in situ hybridization was particularly useful for tumors with lymphoplasmacytoid morphology but performed poorly in lymphomas having no plasmacytic differentiation. κ/λ immunohistochemistry showed no additional usefulness when applied together with κ/λ in situ hybridization. Immunoglobulin gene rearrangement studies by polymerase chain reaction achieved high detection rates of clonality in all cytomorphologic subgroups.

CONCLUSIONS.—

Our study offers a practical evaluation of common diagnostic tests in pulmonary MALT lymphoma. We offer recommendations for a diagnostic workup that takes into consideration the usefulness and the specific limitations of the various diagnostic strategies.

EBV-positive Nodal T-Cell and NK-Cell Lymphoma: A Study of 26 Cases Including a Subset With Strong CD30 Expression Mimicking Anaplastic Large Cell Lymphoma

Epstein-Barr virus (EBV)-positive nodal T-cell and NK-cell lymphoma is a rare neoplasm of cytotoxic T-cell or NK-cell lineage. Here, we report 26 cases affecting 14 men and 12 women with a median age of 52 years. All patients presented with disease involving multiple lymph nodes, and 20 of 22 (91%) fully staged patients had advanced Ann Arbor stage disease. Spleen, liver, and bone marrow were involved in 70%, 50%, and 52% of cases, respectively. These patients had a dismal prognosis with a median survival of 30 days. Histologically, lymph nodes were replaced by lymphoma in a diffuse pattern. Lymphoma cells were variable in size and large cell morphology was seen in 62% of cases. The neoplastic cells were CD4-/CD8- in 14 (54%) cases and CD4-/CD8+ in 12 (46%) cases. CD56 was positive in 14 (54%) cases. CD30 was positive in 20 (77%) cases; a strong and diffuse pattern was observed in 14 (54%) cases, mimicking, in part, anaplastic large cell lymphoma (ALCL). CD30 expression was associated with younger age and large cell morphology. In summary, EBV+ nodal T-cell and NK-cell lymphoma is an aggressive disease with a poor prognosis. These neoplasms are heterogeneous at the morphologic and immunophenotypic levels. Diffuse and strong expression of CD30 could potentially lead to a misdiagnosis of ALCL if EBV evaluation is not performed. Distinguishing between EBV+ nodal T-cell and NK-cell lymphoma from ALCL is important because treatment strategy and prognosis differ. CD30 expression offers a potential therapeutic target for patients with this aggressive disease.

Unbiased serum metabolomic analysis in cats with naturally occurring chronic enteropathies before and after medical intervention

Chronic enteropathies (CE) are common disorders in cats and the differentiation between the two main underlying diseases, inflammatory bowel disease (IBD) and low-grade intestinal T-cell lymphoma (LGITL), can be challenging. Characterization of the serum metabolome could provide further information on alterations of disease-associated metabolic pathways and may identify diagnostic or therapeutic targets. Unbiased metabolomics analysis of serum from 28 cats with CE (14 cats with IBD, 14 cats with LGITL) and 14 healthy controls identified 1,007 named metabolites, of which 129 were significantly different in cats with CE compared to healthy controls at baseline. Random Forest analysis revealed a predictive accuracy of 90% for differentiating controls from cats with chronic enteropathy. Metabolic pathways found to be significantly altered included phospholipids, amino acids, thiamine, and tryptophan metabolism. Several metabolites were found to be significantly different between cats with IBD versus LGITL, including several sphingolipids, phosphatidylcholine 40:7, uridine, pinitol, 3,4-dihydroxybenzoic acid, and glucuronic acid. However, random forest analysis revealed a poor group predictive accuracy of 60% for the differentiation of IBD from LGITL. Of 129 compounds found to be significantly different between healthy cats and cats with CE at baseline, 58 remained different following treatment.

Evaluation of next-generation sequencing versus next-generation flow cytometry for minimal-residual-disease detection in Chinese patients with multiple myeloma

PURPOSE

To evaluate the efficacy of next-generation sequencing (NGS) in minimal-residual-disease (MRD) monitoring in Chinese patients with multiple myeloma (MM).

METHODS

This study analyzed 60 Chinese MM patients. During MRD monitoring in these patients' post-therapy, clonal immunoglobulin heavy chain (IGH) rearrangements were detected via NGS using LymphoTrack assays. MRD monitoring was performed using NGS or next-generation flow cytometry (NGF), and the results were compared. Additionally, the sensitivity and reproducibility of the NGS method were assessed.

RESULTS

The MRD detection range of the NGS method was 10-6-10-1, which suggested good linearity, with a Pearson correlation coefficient of 0.985 and a limit of detection of 10-6. Intra- and inter-assay reproducibility analyses showed that NGS exhibited 100% reproducibility with low variability in clonal cells. At diagnosis, unique clones were found in 42 patients (70.0%) with clonal IGH rearrangements, which were used as clonality markers for MRD monitoring post-therapy. Comparison of NGS and NGF for MRD monitoring showed 79.1% concordance. No samples that tested MRD-positive via NGF were found negative via NGS, indicating the higher sensitivity of NGS. MRD could be detected using NGS in 6 of 7 samples before autologous hematopoietic stem-cell transplantation, and 5 of them tested negative post-transplantation. In contrast, the NGF method could detect MRD in only 1 sample pre-transplantation.

CONCLUSION

Compared with NGF, NGS exhibits higher sensitivity and reproducibility in MRD detection and can be an effective strategy for MRD monitoring in Chinese MM patients.

Histological criteria for selecting patients who need clonality test for non-gastric MALT lymphoma diagnosis

The histological diagnosis of extranodal marginal zone lymphoma of the mucosa-associated lymphoid tissue (MALT lymphoma) is difficult for pathologists. Recently, digital pathology systems have been widely used to provide tools that can objectively measure lesions on slides. In this study, we measured the extent of marginal zone expansion in suspected MALT lymphoma cases and compared the results with those of a molecular clonality test. In total, 115 patients who underwent an IGH gene rearrangement test for suspected MALT lymphoma were included in this study. All cases were histologically classified into three patterns; "small lymphoid aggregates with no germinal center (Pattern 1)," "lymphoid follicles with germinal center (Pattern 2)" and " fused marginal zone or diffuse small lymphocytic proliferation (Pattern 3)." The proportions of monoclonality in Pattern 1, 2, and 3 were 25.0%, 55.0%, and 97.9%, respectively. The ratios of marginal zone thickness to germinal center diameter and entire lymphoid follicle area to germinal center area were measured in Pattern 2 cases using a digital pathology system. Combining the width cutoff of 1.5 and the areal cutoff of 3.5, the sensitivity, specificity, positive predictive value, and negative predictive value for MALT lymphoma were 96.97%, 70.37%, 80.00%, and 95.00%, respectively. In conclusion, through objective measurement of the marginal zone, suspected cases of MALT lymphoma requiring a molecular clonality test can be effectively selected.

Dual T-cell constant β chain (TRBC)1 and TRBC2 staining for the identification of T-cell neoplasms by flow cytometry

The diagnosis of leukemic T-cell malignancies is often challenging, due to overlapping features with reactive T-cells and limitations of currently available T-cell clonality assays. Recently developed therapeutic antibodies specific for the mutually exclusive T-cell receptor constant β chain (TRBC)1 and TRBC2 isoforms provide a unique opportunity to assess for TRBC-restriction as a surrogate of clonality in the flow cytometric analysis of T-cell neoplasms. To demonstrate the diagnostic utility of this approach, we studied 164 clinical specimens with (60) or without (104) T-cell neoplasia, in addition to 39 blood samples from healthy donors. Dual TRBC1 and TRBC2 expression was studied within a comprehensive T-cell panel, in a fashion similar to the routine evaluation of kappa and lambda immunoglobulin light chains for the detection of clonal B-cells. Polytypic TRBC expression was demonstrated on total, CD4+ and CD8+ T-cells from all healthy donors; and by intracellular staining on benign T-cell precursors. All neoplastic T-cells were TRBC-restricted, except for 8 cases (13%) lacking TRBC expression. T-cell clones of uncertain significance were identified in 17 samples without T-cell malignancy (13%) and accounted for smaller subsets than neoplastic clones (median: 4.7 vs. 69% of lymphocytes, p < 0.0001). Single staining for TRBC1 produced spurious TRBC1-dim subsets in 24 clinical specimens (15%), all of which resolved with dual TRBC1/2 staining. Assessment of TRBC restriction by flow cytometry provides a rapid diagnostic method to detect clonal T-cells, and to accurately determine the targetable TRBC isoform expressed by T-cell malignancies.

Clinical significance of bone marrow involvement by immunoglobulin gene rearrangement in de novo diffuse large B-cell lymphoma: a multicenter retrospective study

Background

Bone marrow (BM) involvement is an indicator of a poor prognosis in diffuse large B-cell lymphoma (DLBCL); however, few studies have evaluated the role of immunoglobulin gene rearrangement (IgR) in detecting BM involvement.

Methods

We evaluated the clinical characteristics and treatment outcomes of patients with DLBCL based on histological BM involvement or positive BM IgR using polymerase chain reaction or next-generation sequencing. We also investigated the role of consolidative upfront autologous hematopoietic stem cell transplantation (ASCT) in patients with DLBCL and BM involvement.

Results

Among 624 patients, 123 (19.7%) with histological BM involvement and 88 (17.5%) with positive IgR in histologically negative BM had more advanced disease characteristics. Overall (OS) and progression-free (PFS) survival was better for patients with negative BM histology and negative IgR than that in patients with histological BM involvement (P = 0.050 and P < 0.001, respectively) and positive IgR with negative BM histology (P = 0.001 and P = 0.005, respectively). Survival rates did not differ among 82 (13.1%) patients who were treated with upfront ASCT and had histological BM involvement or positive IgR with negative BM histology. The survival outcomes were worse for patients who were not treated with upfront ASCT and for those with histological BM involvement or positive IgR, than for those with negative BM histology and negative IgR.

Conclusion

Patients diagnosed with DLBCL and BM involvement based on histology or IgR had aggressive clinical features and poor survival. Upfront ASCT mitigated poor prognosis due to BM involvement.

Pathology for severe inflammatory PML with PD1/PD-L1 expression of favorable prognosis: What's a prognostic factor for PML-IRIS?

A 72-year-old woman with dermatomyositis (DM) developed neurological manifestation, and magnetic resonance imaging (MRI) revealed multiple T2/fluid-attenuated inversion recovery (FLAIR)-hyperintense lesions predominantly in the deep white matter of the cerebral hemisphere. Punctate or linear contrast enhancement was observed surrounding the T1-hypointense area. Multiple T2/FLAIR-hyperintense lesions were aligned along with the corona radiata. Malignant lymphoma was first suspected, and a brain biopsy was performed. Pathological investigation suggested the provisional diagnosis of "suspicious of malignant lymphoma." Owing to emergent clinical conditions, high-dose methotrexate (MTX) therapy was conducted, and then T2/FLAIR-hyperintense lesions were dramatically reduced. However, the diagnosis of malignant lymphoma was concerning since multiplex PCR demonstrated clonal restriction of the Ig H gene for B cells and TCR beta genes for T cells. Histopathology revealed the infiltration of both CD4+ and CD8+ T cells, and the CD4+ /CD8+ ratio was 4.0. Moreover, prominent plasma cells were observed, in addition to CD20+ B cells. Atypical cells with enlarged nuclei were present, and they were not hematopoietic but found as glial cells. JC virus (JCV) infection was verified with both immunohistochemistry and in situ hybridization; the final diagnosis was progressive multifocal leukoencephalopathy (PML). The patient was treated with mefloquine and discharged. This case is informative in understanding the host anti-viral response. Variable inflammatory cells were observed, including CD4+ and CD8+ T cells, plasma cells, and a small amount of perivascular CD20+ B cells. PD-1 and PD-L1 expression was observed in lymphoid cells and macrophages, respectively. PML with inflammatory reactions was thought fatal, and autopsy cases of PML with immune reconstitution inflammatory syndrome (IRIS) demonstrated excessive infiltration of only CD8+ T cells. However, this case revealed infiltration of variable inflammatory cells, and a favorable prognosis would be expected under PD-1/PD-L1 immune-checkpoint regulation.

Diagnostic and prognostic molecular pathology of lymphoid malignancies

With the explosion in knowledge about the molecular landscape of lymphoid malignancies and the increasing availability of high throughput techniques, molecular diagnostics in hematopathology has moved from isolated marker studies to a more comprehensive approach, integrating results of multiple genes analyzed with a variety of techniques on the DNA and RNA level. Although diagnosis of lymphoma still relies on the careful integration of clinical, morphological, phenotypic, and, if necessary molecular features, and only few entities are defined strictly by genetic features, genetic profiling has contributed profoundly to our current understanding of lymphomas and shaped the two current lymphoma classifications, the International Consensus Classification and the fifth edition of the WHO classification of lymphoid malignancies. In this review, the current state of the art of molecular diagnostics in lymphoproliferations is summarized, including clonality analysis, mutational studies, and gene expression profiling, with a focus on practical applications for diagnosis and prognostication. With consideration for differences in accessibility of high throughput techniques and cost limitations, we tried to distinguish between diagnostically relevant and in part disease-defining molecular features and optional, more extensive genetic profiling, which is usually restricted to clinical studies, patients with relapsed or refractory disease or specific therapeutic decisions. Although molecular diagnostics in lymphomas currently is primarily done for diagnosis and subclassification, prognostic stratification and predictive markers will gain importance in the near future.

Primary anaplastic lymphoma kinase-positive large B-cell lymphoma of the left bulbar conjunctiva: A case report

BACKGROUND

Anaplastic lymphoma kinase (ALK)-positive large B-cell lymphoma (LBCL) is an aggressive and rare variant of diffuse LBCL. Herein, we report an uncommon case of stage IE extranodal ALK-positive LBCL initially originating in the bulbar conjunctiva.

CASE SUMMARY

A 63-year-old woman presented with a mass in the left bulbar conjunctiva that had persisted for six months, accompanied by swelling and pain that had persisted for 3 d. Eye examination revealed an 8 mm slightly elevated pink mass in the lower conjunctival sac of the left eye. Microscopically, the tumor was composed of large immunoblastic and plasmablastic large lymphoid cells with scattered anaplastic or multinucleated large cells. Immunophenotypically, the neoplastic cells were positive for ALK, CD10, CD138, Kappa, MUM1, BOB.1, OCT-2, CD4, CD45, EMA, CD79a, CD38, and AE1/AE3, and negative for CD20, PAX5, Lambda, BCL6, CD30 and all other T-cell antigens. The results of gene rearrangement tests showed monoclonal IGH/IGK/IGL and TCRD rearrangements. Fluorescence in situ hybridization studies did not reveal any BCL2, BCL6 or MYC rearrangements. Furthermore, Epstein-Barr virus was not detected by in situ hybridization in the lesions. Based on the histopathological and imaging examinations, the neoplasm was classified as stage IE ALK-positive LBCL. No further treatments were administered. At the 6, 15, and 21 mo postoperative follow-up visits, the patient was in good condition, without obvious discomfort. This case represents the first example of primary extranodal ALK-positive LBCL presenting as a bulbar conjunctival mass, which is extremely rare and shares morphological and immunohistochemical features with a variety of other neoplasms that can result in misdiagnosis.

CONCLUSION

Awareness of the condition presented in this case report is necessary for early and accurate diagnosis and appropriate treatment.

Molecular pathology assists the diagnosis of lymphoepithelial sialadenitis, Sjögren's syndrome and extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue

Background/purpose

Lymphoepithelial sialadenitis (LESA), Sjögren's syndrome (SS), and salivary MALT lymphoma are diseases characterized by lymphoepithelial lesions, and the differential diagnosis between them in the salivary glands is challenging. This study aimed to explore clinicopathological and genetic characteristics of the three diseases.

Materials and methods

We retrospectively analyzed the clinical features, the histomorphology, immunohistochemistry, and genetic profiling by polymerase chain reaction (PCR) and next-generation sequencing (NGS).

Results

There included 68 LESAs, 25 SSs, and 62 MALT lymphomas. Ten cases relapsed in total, and 3 of MALT lymphomas died due to high-level transformation. Immunohistochemical double staining showed FCRL4 cells co-expressed Pax-5 and Ki-67, suggesting FCRL4 cells were proliferative B-cells. The expression level of the FCRL4 was significantly higher in MALT lymphoma than LESA and SS. The detection rates of clonal IGH, IGK, and IGL gene rearrangements in MALT lymphoma with a sensitivity of 83.33%. Monoclonal immunoglobulin gene rearrangements were confirmed in five suspected patients by NGS (100%).

Conclusion

FCRL4 B cells might play an important role in the formation of lymphoepithelial lesions and might be as a diagnostic positive marker of salivary MALT lymphoma. The application of multiple detection methods could significantly improve the diagnostic accuracy for MALT lymphomas from LESA and SS.

Chronic Inflammatory Enteropathy and Low-Grade Intestinal T-Cell Lymphoma Are Associated with Altered Microbial Tryptophan Catabolism in Cats

Chronic inflammatory enteropathy (CIE) and low-grade intestinal T-cell lymphoma (LGITL) are common chronic enteropathies (CE) in cats. Enteric microbiota dysbiosis is implicated in the pathogenesis of CE; however, the mechanisms of host-microbiome interactions are poorly understood in cats. Microbial indole catabolites of tryptophan (MICT) are gut bacterial catabolites of tryptophan that are hypothesized to regulate intestinal inflammation and mucosal barrier function. MICTs are decreased in the sera of humans with inflammatory bowel disease and previous studies identified altered tryptophan metabolism in cats with CE. We sought to determine whether MICTs were decreased in cats with CE using archived serum samples from cats with CIE (n = 44) or LGITL (n = 31) and healthy controls (n = 26). Quantitative LC-MS/MS was used to measure serum concentrations of tryptophan, its endogenous catabolites (kynurenine, kynurenate, serotonin) and MICTs (indolepyruvate, indolealdehyde, indoleacrylate, indoleacetamide, indoleacetate, indolelactate, indolepropionate, tryptamine). Serum concentrations of tryptophan, indolepropionate, indoleacrylate, indolealdehyde, indolepyruvate, indolelactate were significantly decreased in the CIE and LGITL groups compared to those in healthy controls. Indolelactate concentrations were significantly lower in cats with LGITL compared to CIE (p = 0.006). Significant correlations were detected among serum MICTs and cobalamin, folate, fPLI, and fTLI. Our findings suggest that MICTs are promising biomarkers to investigate the role of gut bacteria in the pathobiology of chronic enteropathies in cats.

Portal hypertension in common variable immunodeficiency disorders - a single center analysis on clinical and immunological parameter in 196 patients

Background

Liver manifestations and in particular portal hypertension (PH) contribute significantly to morbidity and mortality of patients with common variable immunodeficiency disorders (CVID). Screening strategies and early detection are limited due to the lack of specific diagnostic tools.

Methods

We evaluated clinical, immunological, histological, and imaging parameters in CVID patients with clinical manifestation of portal hypertension (CVID+PH).

Results

Portal hypertension was present in 5.6% of CVID patients and was associated with high clinical burden and increased mortality (18%). Longitudinal data on clinical and immunological parameters in patients before and during clinically manifest portal hypertension revealed a growing splenomegaly and increasing gamma-glutamyl transferase (GGT) and soluble interleukin 2 receptor (SIL-2R) levels with decreasing platelets over time. While ultrasound of the liver failed to detect signs of portal hypertension in most affected patients, transient elastography was elevated in all patients. All CVID+PH patients had reduced naïve CD45RA+CD4+ T-cells (mean of 6,2%). The frequency of severe B-lymphocytopenia (Euroclass B-) was higher in CVID+PH patients. The main histological findings included lymphocytic infiltration, nodular regenerative hyperplasia-like changes (NRH-LC), and porto(-septal) fibrosis.

Conclusion

CVID patients with lower naïve CD45RA+CD4+ T-cells or severely reduced B-cells might be at higher risk for portal hypertension. The combination of biochemical (increasing sIL-2R, GGT, and decreasing platelets) and imaging parameters (increasing splenomegaly) should raise suspicion of the beginning of portal hypertension.

Plasmablastic transformation of chronic lymphocytic leukemia: a review of literature and report on 2 cases

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is the most common leukemia in adults in Western countries. Transformation of CLL/SLL to plasmablastic lymphoma (PBL) is exceedingly rare and often has an extremely poor response to treatment. A thorough molecular workup may help in determining clonality-relatedness and prognosis. We describe two cases of CLL/SLL that transformed into PBL, with an extensive molecular workup in one case, and a review of the literature.

Updates on lymphoblastic leukemia/lymphoma classification and minimal/measurable residual disease analysis

Lymphoblastic leukemia/lymphoma (ALL/LBL), especially certain subtypes, continues to confer morbidity and mortality despite significant therapeutic advances. The pathologic classification of ALL/LBL, especially that of B-ALL, has recently substantially expanded with the identification of several distinct and prognostically important genetic drivers. These discoveries are reflected in both current classification systems, the World Health Organization (WHO) 5th edition and the new International Consensus Classification (ICC). In this article, novel subtypes of B-ALL are reviewed, including DUX4, MEF2D and ZNF384-rearranged B-ALL; the rare pediatric entity B-ALL with TLF3::HLF, now added to the classifications, is discussed; updates to the category of B-ALL with BCR::ABL1-like features (Ph-like B-ALL) are summarized; and emerging genetic subtypes of T-ALL are presented. The second half of the article details current approaches to minimal/measurable residual disease (MRD) detection in B-ALL and T-ALL and presents anticipated challenges to current approaches in the burgeoning era of antigen-directed immunotherapy.

Clonal Relationship and Mutation Analysis in Lymphoplasmacytic Lymphoma/Waldenström Macroglobulinemia Associated With Diffuse Large B-cell Lymphoma

Patients with lymphoplasmacytic lymphoma/Waldenström macroglobulinemia (LPL/WM) occasionally develop diffuse large B-cell lymphoma (DLBCL). This mostly results from LPL/WM transformation, although clonally unrelated DLBCL can also arise. LPL/WM is characterized by activating MYD88L265P (>95%) and CXCR4 mutations (~30%), but the genetic drivers of transformation remain to be identified. Here, in thirteen LPL/WM patients who developed DLBCL, the clonal relationship of LPL and DLBCL together with mutations contributing to transformation were investigated. In 2 LPL/WM patients (15%), high-throughput sequencing of immunoglobulin gene rearrangements showed evidence of >1 clonal B-cell population in LPL tissue biopsies. In the majority of LPL/WM patients, DLBCL presentations were clonally related to the dominant clone in LPL, providing evidence of transformation. However, in 3 patients (23%), DLBCL was clonally unrelated to the major malignant B-cell clone in LPL, of which 2 patients developed de novo DLBCL. In this study cohort, LPL displayed MYD88L265P mutation in 8 out of eleven patients analyzed (73%), while CXCR4 mutations were observed in 6 cases (55%). MYD88WT LPL biopsies present in 3 patients (27%) were characterized by CD79B and TNFAIP3 mutations. Upon transformation, DLBCL acquired novel mutations targeting BTG1, BTG2, CD79B, CARD11, TP53, and PIM1. Together, we demonstrate variable clonal B-cell dynamics in LPL/WM patients developing DLBCL, and the occurrence of clonally unrelated DLBCL in about one-quarter of LPL/WM patients. Moreover, we identified commonly mutated genes upon DLBCL transformation, which together with preserved mutations already present in LPL characterize the mutational landscape of DLBCL occurrences in LPL/WM patients.

Genetic abnormalities assist in pathological diagnosis and EBV-positive cell density impact survival in Chinese angioimmunoblastic T-cell lymphoma patients

Objective

To explore the application of genetic abnormalities in the diagnosis of angioimmunoblastic T-cell lymphoma (AITL) and the reliable pathological prognostic factors.

Methods

This study included 53 AITL cases, which were reviewed for morphological patterns, immunophenotypes, presence of Hodgkin and Reed-Sternberg (HRS)-like cells, and co-occurrence of B cell proliferation. The Epstein-Barr virus (EBV)-positive cells in tissues were counted, and cases were classified into "EBV encoded RNA (EBER) high-density" group if >50/HPF. Targeted exome sequencing was performed.

Results

Mutation data can assist AITL diagnosis: 1) with considerable HRS-like cells (20 cases): RHOA mutated in 14 cases (IDH2 co-mutated in 3 cases, 4 cases with rare RHOA mutation), TET2 was mutated in 5 cases (1 case co-mutated with DNMT3A), and DNMT3A mutated in 1 case; 2) accompanied with B cell lymphoma (7 cases): RHOA mutated in 4 cases (1 case had IDH2 mutation), TET2 mutated in 2 cases and DNMT3A mutated in 1 case; 3) mimic peripheral T cell lymphoma, not otherwise specified (5 cases): RHOA mutated in 2 cases (IDH2 co-mutated in 1 case), TET2 mutated in 3 cases, and DNMT3A mutated in 1 case; 4) pattern 1 (1 case), RHOA and TET2 co-mutated. Besides RHOAG17V (30/35), rare variant included RHOAK18N, RHOAR68H, RHOAC83Y, RHOAD120G and RHOAG17del, IDH2R172 co-mutated with IDH2M397V in one case. There were recurrent mutations of FAT3, PCLO and PIEZO1 and genes of epigenetic remodeling, T-cell activation, APC and PI3K/AKT pathway. EBER high-density independently indicated adverse overall survival and progression-free survival (P=0.046 and P=0.008, Kaplan-Meier/log-rank).

Conclusions

Over half AITL cases might be confused in diagnosis for certain conditions without mutation data. Targeted exome sequencing with a comprehensive panel is crucial to detect both hot-spot and rare mutation variants for RHOA and IDH2 and other recurrent mutated genes in addition to TET2 and DNMT3A. EBER high-density independently indicated adverse survival.

EuroClonality-NGS Recommendations for Evaluation of B-Cell Clonality Analysis by Next-Generation Sequencing: A Structured Approach with the DEPART Algorithm

Next-generation sequencing (NGS)-based clonality analysis allows in-depth assessment of the clonal composition of a sample with high sensitivity for detecting small clones. Within the EuroClonality-NGS Working Group, a protocol for NGS Ig clonality analysis was developed and validated previously. This NGS-based approach was designed to generate small amplicons, making it suitable for samples with suboptimal DNA quality, especially material derived from formalin-fixed, paraffin-embedded tissue. Using expert assessment of NGS Ig clonality results as a reference, a structured algorithmic approach to the assessment of NGS-amplicon-based B-cell clonality analysis was developed. A structured approach with the Detection of clonality through Evaluation of sample quality and assessment of Pattern, Abundance and RaTio (DEPART) algorithm was proposed, which consecutively evaluates sample quality, the pattern of the clonotypes present, the abundance of the most dominant clonotypes, and the ratio between the dominant clonotypes and the background to evaluate the different Ig gene targets. Specific issues with respect to evaluation of the various Ig targets as well as the integration of results of individual targets into a molecular clonality conclusion are discussed and illustrated with case examples. Finally, the importance of interpretation of NGS-based clonality results in clinical and histopathologic contexts is discussed. It is expected that these recommendations will have clinical utility to facilitate proper evaluation of clonality assessment.

The clinical and molecular taxonomy of t(14;18)-negative follicular lymphomas

Follicular lymphoma (FL) is a neoplasm derived from germinal center B cells, composed of centrocytes and centroblasts, with at least a focal follicular growth pattern. The t(14;18) translocation together with epigenetic deregulation through recurrent genetic alterations are now recognized as the hallmark of FL. Nevertheless, FL is a heterogeneous disease, clinically, morphologically, and biologically. The existence of FL lacking the t(14;18) chromosomal alteration highlights the complex pathogenesis of FL, and indicates that there are alternative pathogenetic mechanisms that can induce a neoplasm with follicular center B-cell phenotype. Based on their clinical presentation, t(14;18)-negative FLs can be divided into 3 broad groups: nodal presentation, extranodal presentation, and those affecting predominantly children and young adults. Recent studies have shed some light into the genetic alterations of t(14;18)-negative FL. Within the group of t(14;18)-negative FL with nodal presentation, cases with STAT6 mutations are increasingly recognized as a distinctive molecular subgroup, often cooccurring with CREBBP and/or TNFRSF14 mutations. FL with BCL6 rearrangement shows clinicopathological similarities to its t(14;18)-positive counterpart. In contrast, t(14;18)-negative FL in extranodal sites is characterized mainly by TNFRSF14 mutations in the absence of chromatin modifying gene mutations. FL in children have a unique molecular landscape when compared with those in adults. Pediatric-type FL (PTFL) is characterized by MAP2K1, TNFRSF14, and/or IRF8 mutations, whereas large B-cell lymphoma with IRF4 rearrangement is now recognized as a distinct entity, different from PTFL. Ultimately, a better understanding of FL biology and heterogeneity should help to understand the clinical differences and help guide patient management and treatment decisions.

Single-Step IGHV Next-Generation Sequencing Detects Clonality and Somatic Hypermutation in Lymphoid Malignancies: A Phase III Diagnostic Accuracy Study

BACKGROUND

Multiplex PCR based on consensus primers followed by capillary electrophoresis and Sanger sequencing are considered as the gold standard method for the evaluation of clonality and somatic hypermutation in lymphoid malignancies. As an alternative, the next-generation sequencing (NGS) of immune receptor genes has recently been proposed as a solution, due to being highly effective and sensitive. Here, we designed a phase III diagnostic accuracy study intended to compare the current gold standard methods versus the first commercially available NGS approaches for testing immunoglobulin heavy chain gene rearrangements.

METHODS

We assessed IGH rearrangements in 68 samples by means of both the NGS approach (LymphoTrack® IGH assay, and LymphoTrack® IGH somatic hypermutation assay, run on Illumina MiSeq) and capillary electrophoresis/Sanger sequencing to assess clonality and somatic hypermutations (SHM).

RESULTS

In comparison to the routine capillary-based analysis, the NGS clonality assay had an overall diagnostic accuracy of 96% (63/66 cases). Other studied criteria included sensitivity (95%), specificity (100%), positive predictive value (100%) and negative predictive value (75%). In discrepant cases, the NGS results were confirmed by a different set of primers that provided coverage of the IGH leader sequence. Furthermore, there was excellent agreement of the SHM determination with both the LymphoTrack® FR1 and leader assays when compared to the Sanger sequencing analysis (84%), with NGS able to assess the SHM rate even in cases where the conventional approach failed.

CONCLUSION

Overall, conventional Sanger sequencing and next-generation-sequencing-based clonality and somatic hypermutation analyses gave comparable results. For future use in a routine diagnostic workflow, NGS-based approaches should be evaluated prospectively and an analysis of cost-effectiveness should be performed.

Unusual localization and clinical presentation of primary central nervous system extranodal marginal zone B‑cell lymphoma: A case report

Primary central nervous system (CNS) extranodal marginal zone B-cell lymphoma (MZBL) is a rare low-grade non-Hodgkin lymphoma, characterised predominantly by small B cells, plasma cells, monocytoid cells and scattered large immunoblasts. Primary CNS MZBL is a slow-growing tumour that remains localised and is characterised by an excellent clinical prognosis. The present study describes the case of a 48-year-old HIV-negative female patient with a history of head trauma 1 year prior, who presented with worsening neurological symptoms and a magnetic resonance imaging finding of a ~3-cm extra-axial mass within the left lateral ventricle. From histopathology and immunohistochemistry, the lesion was diagnosed as a CNS MZBL; as no other primary lesions were found, the base of the choroid plexuses of the left lateral ventricle was considered the primary site. To the best of our knowledge, the current case is the first study to report on primary CNS MZBL arising in this anatomical site and paves the way for further studies on the role of chronic inflammation (in the present case resulting from trauma) in the pathogenesis not only of primary CNS MZBL but also of lymphoma in general. Additionally, this report could serve as a starting point for studies analysing the role of meningothelial cells in the pathogenesis of primary CNS MZBL.

Serological and Molecular Characterization of Hepatitis C Virus-Related Cryoglobulinemic Vasculitis in Patients without Cryoprecipitate

Prolonged B cells stimulation due to the Hepatitis C virus (HCV) can result in autoimmunity, stigmatized by rising levels of cryoglobulins (CGs), the rheumatoid factor (RF), and free light chains (FLC) of immunoglobulins (Ig) associated with a range of symptoms, from their absence to severe cryoglobulinemic vasculitis and lymphoma. Here, we aimed to identify an immunological signature for the earliest stages of vasculitis when cryoprecipitate is still not detectable. We firstly analyzed the IgG subclasses, FLC, and RF in 120 HCV-RNA-positive patients divided into four groups according to the type of cryoprecipitate and symptoms: 30 asymptomatic without cryoprecipitate (No Cryo), 30 with vasculitis symptoms but without CGs that we supposed were circulating but still not detectable (Circulating), 30 type II and 30 type III mixed cryoglobulinemia (Cryo II and Cryo III, respectively). Our results revealed that patients with supposed circulating CGs displayed a pattern of serological parameters that closely resembled Cryo II and Cryo III, with a stronger similarity to Cryo II. Accordingly, we analyzed the groups of Circulating and Cryo II for their immunoglobulin heavy chain (IgH) and T-cell receptor (TCR) gene rearrangements, finding a similar mixed distribution of monoclonal, oligoclonal, and polyclonal responses compared to a control group of ten HCV-RNA-negative patients recovered from infection, who displayed a 100% polyclonal response. Our results strengthened the hypothesis that circulating CGs are the origin of symptoms in HCV-RNA-positive patients without cryoprecipitate and demonstrated that an analysis of clonal IGH and TCR rearrangements is the best option for the early diagnosis of extrahepatic complications.

How molecular advances may improve the diagnosis and management of PTCL patients

Peripheral T-cell lymphomas (PTCL) comprised more than 30 rare heterogeneous entities, representing 10 to 15% of adult non-Hodgkin lymphomas. Although their diagnosis is still mainly based on clinical, pathological, and phenotypic features, molecular studies have allowed for a better understanding of the oncogenic mechanisms involved and the refinement of many PTCL entities in the recently updated classifications. The prognosis remains poor for most entities (5-year overall survival < 30%), with current conventional therapies based on anthracyclin-based polychemotherapy regimen, despite many years of clinical trials. The recent use of new targeted therapies appears to be promising for relapsed/refractory patients, such as demethylating agents in T-follicular helper (TFH) PTCL. However further studies are needed to evaluate the proper combination of these drugs in the setting of front-line therapy. In this review, we will summarize the oncogenic events for the main PTCL entities and report the molecular targets that have led to the development of new therapies. We will also discuss the development of innovative high throughput technologies that aid the routine workflow for the histopathological diagnosis and management of PTCL patients.

Clonal Characterization and Somatic Hypermutation Assessment by Next-Generation Sequencing in Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma: A Detailed Description of the Technical Performance, Clinical Utility, and Platform Comparison

Somatic hypermutation status of the IGHV gene is essential for treating patients with chronic lymphocytic leukemia/small lymphocytic lymphoma. Unlike the conventional low-throughput method, assessment of somatic hypermutation by next-generation sequencing (NGS) has potential for uniformity and scalability. However, it lacks standardization or guidelines for routine clinical use. We critically assessed the performance of an amplicon-based NGS assay across 458 samples. Using a validation cohort (35 samples), the comparison of two platforms (Ion Torrent versus Illumina) and two primer sets [leader versus framework region 1 (FR1)] in their ability to identify clonotypic IGHV rearrangement(s) revealed 97% concordance. The mutation rates were identical by both platforms when using the same primer set (FR1), whereas a slight overestimation bias (+0.326%) was found when comparing FR1 with leader primers. However, for nearly all patients this did not affect the stratification into mutated or unmutated categories, suggesting that use of FR1 may provide comparable results if leader sequencing is not available and allowing for a simpler NGS laboratory workflow. In routine clinical practice (423 samples), the productive rearrangement was successfully detected by either primer set (leader, 97.7%; FR1, 94.7%), and a combination of both in problematic cases reduced the failure rate to 1.2%. Higher sensitivity of the NGS-based analysis also detected a higher frequency of double IGHV rearrangements (19.1%) compared with traditional approaches.

ACVIM consensus statement guidelines on diagnosing and distinguishing low-grade neoplastic from inflammatory lymphocytic chronic enteropathies in cats

BACKGROUND

Lymphoplasmacytic enteritis (LPE) and low-grade intestinal T cell lymphoma (LGITL) are common diseases in older cats, but their diagnosis and differentiation remain challenging.

OBJECTIVES

To summarize the current literature on etiopathogenesis and diagnosis of LPE and LGITL in cats and provide guidance on the differentiation between LPE and LGITL in cats. To provide statements established using evidence-based approaches or where such evidence is lacking, statements based on consensus of experts in the field.

ANIMALS

None.

METHODS

A panel of 6 experts in the field (2 internists, 1 radiologist, 1 anatomic pathologist, 1 clonality expert, 1 oncologist) with the support of a human medical immunologist, was formed to assess and summarize evidence in the peer-reviewed literature and complement it with consensus recommendations.

RESULTS

Despite increasing interest on the topic for clinicians and pathologists, few prospective studies were available, and interpretation of the pertinent literature often was challenging because of the heterogeneity of the cases. Most recommendations by the panel were supported by a moderate or low level of evidence. Several understudied areas were identified, including cellular markers using immunohistochemistry, genomics, and transcriptomic studies.

CONCLUSIONS AND CLINICAL IMPORTANCE

To date, no single diagnostic criterion or known biomarker reliably differentiates inflammatory lesions from neoplastic lymphoproliferations in the intestinal tract of cats and a diagnosis currently is established by integrating all available clinical and diagnostic data. Histopathology remains the mainstay to better differentiate LPE from LGITL in cats with chronic enteropathy.

Misdiagnosis analysis of 2291 cases of haematolymphoid neoplasms

Objective

To retrospectively analyze the reasons for misdiagnosis of haematolymphoid neoplasms and provide experience for improving the diagnostic level in China.

Methods

A retrospective analysis was performed on 2291 cases of haematolymphoid diseases evaluated by the Department of Pathology of our hospital from 1 July 2019 to 30 June 2021. All 2291 cases were reviewed by two hematopathologist experts and classified according to the 2017 revised WHO classification criteria, supplemented immunohistochemistry (IHC), molecular biology and genetic information as needed. The diagnostic discordance between primary and expert review was evaluated. The possible causes of the diagnostic discrepancies were analyzed for each step involved in the procedure of diagnosis.

Results

In total, 912 cases did not conform to the expert diagnoses among all the 2291 cases, with a total misdiagnosis rate of 39.8%. Among them, misdiagnosis between benign and malignant lesions accounted for 24.3% (222/912), misdiagnosis between haematolymphoid neoplasms and non-haematolymphoid neoplasms accounted for 3.3% (30/912), misdiagnosis among lineages accounted for 9.3% (85/912), misclassification in lymphoma subtypes accounted for 60.8% (554/912), and other misdiagnoses among benign lesions accounted for 2.3% (21/912) of cases, among which misclassification of lymphoma subtypes was the most common.

Conclusion

The accurate diagnosis of haematolymphoid neoplasms is challenging, involving various types of misdiagnosis and complicated causes, however, it is important for precise treatment. Through this analysis, we aimed to highlight the importance of accurate diagnosis, avoid diagnostic pitfalls and to improve the diagnostic level in our country.

Challenges in the Diagnosis of Epstein-Barr Virus-positive Inflammatory Follicular Dendritic Cell Sarcoma: Extremely Wide Morphologic Spectrum and Immunophenotype

Epstein-Barr virus (EBV)-positive inflammatory follicular dendritic cell (FDC) sarcoma (EBV + IFDCS) is a rare entity, and its histopathological characteristics have not been fully described. Here, we investigated the wide morphologic spectrum and immunophenotype of this tumor with the aim to help avoid misdiagnosis. Thirteen cases of EBV + IFDCS were retrospectively analyzed, combined with a review of 70 cases reported in the literature. The median age of patients was 49 (range, 29 to 67 y). Six patients were male and 7 were female. Most cases (92.3%, 12/13) occurred in the liver or spleen, and only 1 case affected an extra-hepatosplenic site (lung, 7.7%, 1/13). Tumors were assessed for a variety of histologic features and assigned to the following morphologic groups: classic type (53.8%, 7/13), lymphoma-like subtype (38.5%, 5/13), and hemangioma-like subtype (7.7%, 1/13). The classic type had distinct EBV-positive neoplastic cells with a fascicular or storiform growth pattern, variable lymphoplasmacytic infiltrates, and blood vessels. The lymphoma-like subtype had extremely prominent lymphoplasmacytic infiltrates (resembling marginal zone lymphoma with plasmacytoid differentiation) with singly dispersed distinct EBV-positive neoplastic cells, highlighted by in situ hybridization for EBV-encoded small RNA. The hemangioma-like subtype had extremely prominent blood vessels with hyaline and/or fibrinoid degeneration, singly dispersed distinct EBV-positive neoplastic cells, and limited lymphoplasmacytic infiltrates. Immunohistochemically, the neoplastic cells showed variable staining for FDC markers (CD21, CD35, CD23, and SSTR2) and the fibroblastic marker SMA, with the staining ranging from very focal to extensive. The number of EBV-positive neoplastic cells ranged from 80 to 400/HPF. All cases showed variable expression of PD-ligand 1 (PD-L1) (CPS: 5-90). IgG4-positive cells ranged from rare up to 100/HPF. Interestingly, 2 cases satisfied the criteria proposed in a previous study, mimicking IgG4-related disease. EBV + IFDCS is an entity with an extremely wide morphologic spectrum and immunophenotype. Awareness of the spectrum of morphologic presentations of this rare tumor, specifically the lymphoma-like subtype and hemangioma-like subtype, is important for accurate diagnosis.

Combining MYD88 L265P mutation detection and clonality determination on CSF cellular and cell-free DNA improves diagnosis of primary CNS lymphoma

Diagnosis of primary central nervous system lymphoma (PCNSL) is challenging, and although brain biopsy remains the gold standard, cerebrospinal fluid (CSF) constitutes a less invasive source of lymphomatous biomarkers. In a retrospective cohort of 54 PCNSL cases tested at diagnosis or relapse, we evaluated the contribution of immunoglobulin heavy chain (IGH) gene clonality and MYD88 L265P detection on both CSF cell pellets and supernatants, in comparison with cytology, flow cytometry, interleukin (IL)-10 and IL-6 quantification. Clonality assessment included a new assay to detect partial IGH-DJ rearrangements. Clonal IGH rearrangements and/or MYD88 L265P mutation were detected in 27 (50%) cell pellets and 24 (44%) supernatant cell-free (cf) DNA. Combining analyses on both compartments, 36 (66%) cases had at least one detectable molecular marker, present only in cfDNA for 9 (16%) of them. While cytology and flow cytometry were positive in only 7 (13.0%) and 9 (17.3%) cases respectively, high IL-10 levels were observed in 36 (66.7%) cases. Overall, taking into account molecular and cytokine results, 46/54 (85%) cases had at least one lymphomatous biomarker detectable in the CSF. These results show that this combination of biomarkers evaluated on both cell pellet and supernatant CSF fractions improves significantly the biological diagnosis of PCNSL.

Research Topic: Measurable Residual Disease in Hematologic Malignancies. Can digital droplet PCR improve measurable residual disease monitoring in chronic lymphoid malignancies?

Minimal/measurable residual disease (MRD) monitoring is progressively changing the management of hematologic malignancies. The possibility of detecting the persistence/reappearance of disease in patients in apparent clinical remission offers a refined risk stratification and a treatment decision making tool. Several molecular techniques are employed to monitor MRD, from conventional real-time quantitative polymerase chain reaction (RQ-PCR) to next generation sequencing and digital droplet PCR (ddPCR), in different tissues or compartments through the detection of fusion genes, immunoglobulin and T-cell receptor gene rearrangements or disease-specific mutations. RQ-PCR is still the gold standard for MRD analysis despite some limitations. ddPCR, considered the third-generation PCR, yields a direct, absolute, and accurate detection and quantification of low-abundance nucleic acids. In the setting of MRD monitoring it carries the major advantage of not requiring a reference standard curve built with the diagnostic sample dilution and of allowing to reduce the number of samples below the quantitative range. At present, the broad use of ddPCR to monitor MRD in the clinical practice is limited by the lack of international guidelines. Its application within clinical trials is nonetheless progressively growing both in acute lymphoblastic leukemia as well as in chronic lymphocytic leukemia and non-Hodgkin lymphomas. The aim of this review is to summarize the accumulating data on the use of ddPCR for MRD monitoring in chronic lymphoid malignancies and to highlight how this new technique is likely to enter into the clinical practice.

Mutational Profile and Pathological Features of a Case of Interleukin-10 and RGS1-Positive Spindle Cell Variant Diffuse Large B-Cell Lymphoma

Diffuse large B-cell lymphoma with spindle cell morphology is a rare variant. We present the case of a 74-year-old male who initially presented with a right supraclavicular (lymph) node enlargement. Histological analysis showed a proliferation of spindle-shaped cells with narrow cytoplasms. An immunohistochemical panel was used to exclude other tumors, such as melanoma, carcinoma, and sarcoma. The lymphoma was characterized by a cell-of-origin subtype of germinal center B-cell-like (GCB) based on Hans’ classifier (CD10-negative, BCL6-positive, and MUM1-negative); EBER negativity, and the absence of BCL2, BCL6, and MYC rearrangements. Mutational profiling using a custom panel of 168 genes associated with aggressive B-cell lymphomas confirmed mutations in ACTB, ARID1B, DUSP2, DTX1, HLA-B, PTEN, and TNFRSF14. Based on the LymphGen 1.0 classification tool, this case had an ST2 subtype prediction. The immune microenvironment was characterized by moderate infiltration of M2-like tumor-associated macrophages (TMAs) with positivity of CD163, CSF1R, CD85A (LILRB3), and PD-L1; moderate PD-1 positive T cells, and low FOXP3 regulatory T lymphocytes (Tregs). Immunohistochemical expression of PTX3 and TNFRSF14 was absent. Interestingly, the lymphoma cells were positive for HLA-DP-DR, IL-10, and RGS1, which are markers associated with poor prognosis in DLBCL. The patient was treated with R-CHOP therapy, and achieved a metabolically complete response.

Recognizing Minor Leukemic Populations with Monocytic Features in Mixed-Phenotype Acute Leukemia by Flow Cell Sorting Followed by Cytogenetic and Molecular Studies: Report of Five Exemplary Cases

Mixed-phenotype acute leukemia (MPAL), a rare and heterogeneous category of acute leukemia, is characterized by cross-lineage antigen expression. Leukemic blasts in MPAL can be represented either by one population with multiple markers of different lineages or by several single-lineage populations. In some cases, a major blast population may coexist with a smaller population that has minor immunophenotypic abnormalities and may be missed even by an experienced pathologist. To avoid misdiagnosis, we suggest sorting doubtful populations and leukemic blasts and searching for similar genetic aberrations. Using this approach, we examined questionable monocytic populations in five patients with dominant leukemic populations of B-lymphoblastic origin. Cell populations were isolated either for fluorescence in situ hybridization or for clonality assessment by multiplex PCR or next-generation sequencing. In all cases, monocytic cells shared the same gene rearrangements with dominant leukemic populations, unequivocally confirming the same leukemic origin. This approach is able to identify implicit cases of MPAL and therefore leads to the necessary clinical management for patients.

Flow cell sorting followed by PCR-based clonality testing may assist in questionable diagnosis and monitoring of acute lymphoblastic leukemia

INTRODUCTION

Multicolor flow cytometry (MFC) has highly reliable and flexible algorithms for diagnosis and monitoring of acute lymphoblastic leukemia (ALL). However, MFC analysis can be affected by poor sample quality or novel therapeutic options (e.g., targeted therapies and immunotherapy). Therefore, an additional confirmation of MFC data may be needed. We propose a simple approach for validation of MFC findings in ALL by sorting questionable cells and analyzing immunoglobulin/T-cell receptor (IG/TR) gene rearrangements via EuroClonality-based multiplex PCR.

PATIENTS AND METHODS

We obtained questionable MFC results for 38 biological samples from 37 patients. In total, 42 cell populations were isolated by flow cell sorting for downstream multiplex PCR. Most of the patients (n = 29) had B-cell precursor ALL and were investigated for measurable residual disease (MRD); 79% of them received CD19-directed therapy (blinatumomab or CAR-T).

RESULTS

We established the clonal nature of 40 cell populations (95.2%). By using this technique, we confirmed very low MRD levels (<0.01% MFC-MRD). We also applied it to several ambiguous findings for diagnostic samples, including those with mixed-phenotype acute leukemia, and the results obtained impacted the final diagnosis.

CONCLUSION

We have demonstrated possibilities of a combined approach (cell sorting and PCR-based clonality assessment) to validate MFC findings in ALL. The technique is easy to implement in diagnostic and monitoring workflows, as it does not require isolation of a large number of cells and knowledge of individual clonal rearrangements. We believe it provides important information for further treatment.

Diagnostic utility of the lymphoid screening tube supplemented with TRBC1 for the assessment of T-cell clonality

INTRODUCTION

Flow cytometric panels for the investigation of lymphoproliferative disorders, such as the EuroFlow Lymphoid Screening Tube (LST), often fail to demonstrate T-cell clonality, as a suitable clonality marker was unavailable until recently. Aim of this study was to evaluate the added value of supplementing TRBC1, a flow cytometric T-cell clonality marker, to the LST.

METHODS

Flow cytometric analysis was performed on 830 routine samples referred to our lab for suspicion of hematological malignancy. T-cells with monotypic TRBC1-expression were additionally characterized with a 12-color T-cell tube and molecular T-cell receptor gamma gene rearrangement (TRG).

RESULTS

LST analysis revealed 97 (11.7%) samples with the presence of a monotypic T-cell population according to TRBC1, including 21 (2.5%) "high-count" (≥500 cells/μL blood or ≥15% of lymphocytes) and 76 (9.2%) "low-count" (<500 cells/μL blood or <15% of lymphocytes) populations. Clinical symptoms indicative for T-CLPD could be correlated to 11/21 "high-count" and 17/76 "low-count" monotypic T-cell populations. Molecular TRG analysis demonstrated a monoclonal result in 76% (16/21) of "high-count" samples and in 64% (42/66; 10 samples not tested) of "low-count" samples, but also in 9/20 samples with polytypic TRBC1 results.

CONCLUSION

Analysis of an LST tube supplemented with TRBC1 led to the detection of a high number of monotypic T-cell populations. The detection of numerous small monotypic T-cell populations raises the question of their clinical significance. A possible flowchart for assessment of these populations, based on the available literature, is proposed. Molecular TRG analysis is complementary and cannot be omitted from T-cell clonality assessment.

[Nerve biopsy in the diagnosis of peripheral neuropathies]

The indications for nerve biopsy have diminished in recent years. This examination nevertheless remains essential in certain cases of peripheral neuropathies, making it possible to specify the diagnosis or the mechanism of injury for a therapeutic purpose. It is a simple but "invasive" procedure, which can only be performed once on the same nerve. The indications are thus discussed on a case-by-case basis and based on a range of clinical, electrophysiological, biological or even genetic arguments. This involves close collaboration between clinical physicians and pathologists. The main difficulty of this biopsy concerns the fragility of the sample and the techniques necessary for its interpretation, requiring it to be carried out in expert centers. Nerve biopsy is closely related to skin biopsy in the search for small fiber neuropathy. It is a particular technique, but very well codified. The purpose of this review is to recall the indications and contraindications of nerve biopsy, and to explain what the contributions are but also the limits of this examination as well as of skin biopsy.

Reproducibility of low-level residual myeloma immunoglobulin detection using ultra-deep sequencing

Multiple myeloma, a mature B-cell neoplasm, is the second most common hematologic malignancy. Despite advancements in treatment, the disease remains incurable, with more than 100,000 annual deaths worldwide. As recommended by the International Myeloma Working Group, measurable residual disease (MRD) should be addressed at a 10^-5 sensitivity level or beyond for practical purposes. Next-generation sequencing (NGS) has provided new opportunities with deep sequencing of clonal rearrangements of the immunoglobulin heavy chain (IGH) locus in B-cell malignancies. Although the ability to resolve one cancerous cell in a million other B cells is becoming attractive as a prognostic indicator in sustained patients who are MRD-negative, reaching consistent sensitivity levels is challenging because of sample stochasticity and the substantial amount of deoxyribonucleic acid (DNA) required for library preparation. Thus, in the presented study, we implemented ultra-deep sequencing of rearranged IGH to investigate the reproducibility and consistency aimed at the 10^-5 sensitivity level. In this controlled setup, our data provided stable MRD detection of 1.2 clonal cells per 100,000 analyzed cells and longitudinal reproducibility. We also demonstrated a low false-negative rate using 4-5 replicates and 700-800 ng DNA per sequencing replicate. In conclusion, adding an internal control to the replicates enabled clonal cell normalization for MRD evaluation as a stable reference. These findings may guide MRD-level reporting and comparisons between laboratories.

Diagnosis and management of cutaneous lymphomas and lymphoid proliferations in children, adolescents and young adults (CAYA)

Cutaneous lymphomas and lymphoid proliferations (LPD) in children, adolescents, and young adults (CAYA) are a heterogeneous group of lymphoid neoplasms that present formidable diagnostic challenges to clinicians and pathologists alike. Although rare overall, cutaneous lymphomas/LPD occur in real-world settings and awareness of the differential diagnosis, potential complications, and various therapeutic approaches will help ensure the optimal diagnostic work-up and clinical management. Lymphomas/LPD involving the skin can occur as primary cutaneous disease in a patient that characteristically has lymphoma/LPD confined to the skin, or as secondary involvement in patients with systemic disease. This review will comprehensively summarize both primary cutaneous lymphomas/LPD that occur in the CAYA population as well as those CAYA systemic lymphomas/LPD with propensity for secondary cutaneous involvement. Focus on the most common primary entities occurring in CAYA will include lymphomatoid papulosis, primary cutaneous anaplastic large cell lymphoma, mycosis fungoides, subcutaneous panniculitis-like T-cell lymphoma, and hydroa vacciniforme lymphoproliferative disorder.