Application of a 5 Marker Panel to the Routine Diagnosis of Peripheral T-Cell Lymphoma With T-Follicular Helper Phenotype

Implementation of the recommended immunohistochemistry algorithm for classification of peripheral T-cell lymphoma, not otherwise specified into the prognostically significant GATA3 and TBX21 subtypes

INTRODUCTION

Current molecular research has shown the several oncogenic pathways that give rise to the peripheral T-cell lymphoma, not otherwise defined (PTCL, NOS) subtypes, which alter prognosis and might have predictive value. This study was conducted to assess the immunohistochemistry (IHC) algorithm by Amador et al for the subtyping of PTCL, NOS and determine its applicability in relation to the clinicopathological profile.

METHODS

This study included 43 patients with PTCL, NOS diagnosis. Following the use of IHC for the transcription factors GATA3, TBX21, CCR4, and CXCR3, two pathologists subtyped the samples. Comprehensive clinicopathological correlation was carried out.

RESULTS

Applying the algorithm of Amador et al., cases were classified into GATA3 (20), TBX21 (15), and unclassified (8) subtypes. No significant association with clinical parameters of subtypes or CD4/ CD8 positivity was observed. Although a higher proportion of cases in the TBX21 subgroup showed a polymorphic population compared with the GATA3 subgroup, which had a monomorphic population, no significant p-value (0.111) was observed. Two Lennert lymphomas were classified into the GATA3 subgroup. Multivariate analysis showed no significant difference in overall survival (p-value = 0.105) and progression-free survival (p-value = 0.0509) between IHC-defined subtypes; trends indicate that overall survival and progression-free survival are worse in the GATA3 subgroup.

CONCLUSION

Although the algorithm is reproducible, a proportion of cases remains unclassifiable and may require additional investigation and gene expression profiling. The GATA3 subgroup was found to have a monomorphic population with a poor overall prognosis and thus requires a larger sample size for validation.

Clinicopathological implications of immunohistochemical expression of TBX21, CXCR3, GATA3, CCR4, and TCF1 in nodal follicular helper T-cell lymphoma and peripheral T-cell lymphoma, not otherwise specified

BACKGROUND

The classification of nodal peripheral T-cell lymphoma (PTCL) has evolved according to histology, cell-of-origin, and genetic alterations. However, the comprehensive expression pattern of follicular helper T-cell (Tfh) markers, T-cell factor-1 (TCF1), and Th1- and Th2-like molecules in nodal PTCL is unclear.

METHODS

Eighty-two cases of nodal PTCL were classified into 53 angioimmunoblastic T-cell lymphomas (AITLs)/nodal T-follicular helper cell lymphoma (nTFHL)-AI, 18 PTCLs-Tfh/nTFHL-not otherwise specified (NOS), and 11 PTCLs-NOS according to the revised 4th/5th World Health Organization classifications. Immunohistochemistry for TCF1, TBX21, CXCR3, GATA3, and CCR4 was performed.

RESULTS

TCF1 was highly expressed in up to 68% of patients with nTFHL but also in 44% of patients with PTCL-NOS (p > .05). CXCR3 expression was higher in AITLs than in non-AITLs (p = .035), whereas GATA3 expression was higher in non-AITL than in AITL (p = .007) and in PTCL-Tfh compared to AITL (p = .010). Of the cases, 70% of AITL, 44% of PTCLTfh/ nTFHL-NOS, and 36% of PTCL-NOS were subclassified as the TBX21 subtype; and 15% of AITL, 38% of PTCL-Tfh/nTFHL-NOS, and 36% of PTCL-NOS were subclassified as the GATA3 subtype. The others were an unclassified subtype. CCR4 expression was associated with poor progression-free survival (PFS) in patients with PTCL-Tfh (p < .001) and nTFHL (p = .023). The GATA3 subtype showed poor overall survival in PTCL-NOS compared to TBX21 (p = .046) and tended to be associated with poor PFS in patients with non-AITL (p = .054).

CONCLUSIONS

The TBX21 subtype was more prevalent than the GATA3 subtype in AITL. The GATA3 subtype was associated with poor prognosis in patients with non-AITL and PTCL-NOS.

Updates in the Classification of T-cell Lymphomas and Lymphoproliferative Disorders

PURPOSE OF REVIEW

Mature T/NK-cell neoplasms comprise a heterogeneous group of diseases with diverse clinical, histopathologic, immunophenotypic, and molecular features. A clinically relevant, comprehensive, and reproducible classification system for T/NK-cell neoplasms is essential for optimal management, risk stratification, and advancing understanding of these diseases. Two classification systems for lymphoid neoplasms were recently introduced: the 5th edition of World Health Organization classification (WHO-HAEM5) and the 2022 International Consensus Classification (ICC). In this review, we summarize the basic framework and updates in the classification of mature T/NK-cell neoplasms.

RECENT FINDINGS

WHO-HAEM5 and ICC share basic concepts in classification of T/NK-cell neoplasms, emphasizing integration of clinical presentation, pathology, immunophenotype, and genetics. Major updates in both classifications include unifying nodal T-follicular helper-cell lymphomas into a single entity and establishing EBV-positive nodal T/NK-cell lymphoma as a distinct entity. However, some differences exist in taxonomy, terminology, and disease definitions. The recent classifications of mature T/NK-cell neoplasms are largely similar and provide new insights into taxonomy based on integrated clinicopathologic features.

A comparison of the International Consensus and 5th WHO classifications of T-cell lymphomas and histiocytic/dendritic cell tumours

Since the publication in 2017 of the revised 4th Edition of the World Health Organization (WHO) classification of haematolymphoid tumours, here referred to as WHO-HAEM4, significant clinicopathological, immunophenotypic and molecular advances have been made in the field of lymphomas, contributing to refining the diagnostic criteria of several diseases, upgrading entities previously defined as provisional and identifying new entities. This process has resulted in two recent classification proposals of lymphoid neoplasms: the International Consensus Classification (ICC) and the 5th edition of the WHO classification (WHO-HAEM5). In this paper, we review and compare the two classifications in terms of diagnostic criteria and entity definition, focusing on T-cell lymphomas and histiocytic/dendritic cell tumours. Moreover, we update the genetic data of the various pathological entities. The main goal is to provide a tool to facilitate the work of the pathologists, haematologists and researchers involved in the diagnosis and treatment of these haematological malignancies.

Peripheral T-cell lymphoma with a T follicular-helper phenotype: A different entity? Results of the Spanish Real-T study

Nodal peripheral T-cell lymphoma (PTCL) with a T follicular helper phenotype (PTCL-TFH) is a new type of PTCL. We aimed to define its clinical characteristics and prognosis compared to PTCL not otherwise specified (PTCL-NOS) and angioimmunoblastic T-cell lymphoma (AITL). This retrospective observational study included 175 patients diagnosed with PTCL between 2008 and 2013 in 13 Spanish sites. Patient diagnosis was centrally reviewed, and patients were reclassified according to the World Health Organization (WHO) 2016 criteria: 21 patients as PTCL-NOS, 55 as AITL and 23 as PTCL-TFH. Median follow-up was 56.07 months (95% CI 38.7-73.4). Progression-free survival (PFS) and overall survival (OS) were significantly higher in patients with PTCL-TFH than in those with PTCL-NOS and AITL (PFS, 24.6 months vs. 4.6 and 7.8 months, respectively, p = 0.002; OS, 52.6 months vs. 10.0 and 19.3 months, respectively, p < 0.001). Histological diagnosis maintained an independent influence on both PFS (hazard ratio [HR] 4.1 vs. PTCL-NOS, p = 0.008; HR 2.6 vs. AITL, p = 0.047) and OS (HR 5.7 vs. PTCL-NOS, p = 0.004; HR 2.6 vs. AITL, p = 0.096), regardless of the International Prognostic Index. These results suggest that PTCL-TFH could have more favourable features and prognosis than the other PTCL subtypes, although larger series are needed to corroborate these findings.

A Comparison of the Fifth World Health Organization and the International Consensus Classifications of Mature T-Cell Lymphomas

Peripheral T-cell lymphomas (PTCLs) are a rare subset of non-Hodgkin lymphomas that often carry significant difficulty in diagnosis and classification because of their rarity and biological complexity. Previous editions of the World Health Organization (WHO) classifications of hemopoietic neoplasms in 2001, 2008, and 2017 aimed to standardize hemopoietic neoplasm diagnosis in general. Since then, crucial clinico-pathological, immunophenotypic, and recent molecular discoveries have been made in the field of lymphomas, contributing to refining diagnostic criteria of several diseases, upgrading entities previously defined as provisional, and identifying new entities. In 2022, two different models were proposed to classify hematolymphoid neoplasms: the 5th edition of the WHO classification (WHO-HAEM5) and the International Consensus Classification (ICC). Of note, a common nosography is mandatory to ensure progress in health science and ensure the basis for a real precision medicine. In this article, the authors summarized the main differences with the previous fourth WHO edition and reviewed the main discrepancies between the two newest classifications, as far as PTCLs are concerned.

Follicular helper T-cell lymphomas: disease spectrum, relationship with clonal hematopoiesis, and mimics. A report of the 2022 EA4HP/SH lymphoma workshop

Follicular helper T-cell lymphomas (TFH lymphomas) were discussed in session V of the lymphoma workshop of the European Association for Haematopathology (EA4HP)/Society for Hematopathology (SH) 2022 meeting in Florence, Italy. The session focused on the morphologic spectrum of TFH lymphoma, including its three subtypes: angioimmunoblastic-type (AITL), follicular-type, and not otherwise specified (NOS). The submitted cases encompassed classic examples of TFH lymphoma and unusual cases such as those with early or indolent presentations, associated B-cell proliferations, or Hodgkin/Reed-Sternberg-like cells. The relationship between TFH lymphoma and clonal hematopoiesis was highlighted by several cases documenting divergent evolution of myeloid neoplasm and AITL from shared clonal mutations. The distinction between TFH lymphoma and peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS), was stressed, and many challenging examples were presented. Various cases highlighted the difficulties of differentiating TFH lymphoma from other established types of lymphoma and reactive conditions. Cutaneous T-cell lymphoma expressing TFH markers, particularly when resulting in lymph node involvement, should be distinguished from TFH lymphomas. Additional immunophenotyping and next-generation sequencing studies were performed on various cases in this session, highlighting the importance of these technologies to our current understanding and classification of TFH lymphomas.

A Comprehensive Study of the Immunophenotype and its Clinicopathologic Significance in Adult T-Cell Leukemia/Lymphoma

Adult T-cell leukemia/lymphoma (ATLL) is a mature T-cell tumor caused by human T-lymphotropic virus type 1 (HTLV-1). The typical ATLL immunophenotypes are described in the 2017 World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissues (positive: CD2, CD3, CD5, CD4, and CD25; negative: CD7, CD8, and cytotoxic markers; and partially positive: CD30, CCR4, and FOXP3). However, limited studies are available on the expression of these markers, and their mutual relationship remains unknown. Furthermore, the expression status of novel markers associated with T-cell lymphomas, including Th1 markers (T-bet and CXCR3), Th2 markers (GATA3 and CCR4), T follicular helper markers (BCL6, PD1, and ICOS), and T-cell receptor (TCR) markers, and their clinicopathologic significance is unclear. In this study, we performed >20 immunohistochemical stains in 117 ATLL cases to determine the comprehensive immunophenotypic profile of ATLL, which were compared on the basis of clinicopathologic factors, including morphologic variants (pleomorphic vs anaplastic), biopsy locations, treatments, Shimoyama classification-based clinical subtype, and overall survival. CD3+/CD4+/CD25+/CCR4+ was considered a typical immunophenotype of ATLL, but approximately 20% of cases did not conform to this pattern. Simultaneously, the following new findings were obtained: (1) most cases were negative for TCR-β and TCR-δ (104 cases, 88.9%), indicating the usefulness of negative conversion of TCR expression to provide differentiation from other T-cell tumors; (2) the positivity of CD30 and CD15 and the negativity of FOXP3 and CD3 were significantly associated with anaplastic morphology; and (3) atypical cases, such as T follicular helper marker-positive (12 cases, 10.3%) and cytotoxic molecule-positive cases (3 cases, 2.6%), were identified. No single markers could predict the overall survival among patients with acute/lymphoma subtypes of ATLL. The results of this study illustrate the diversity of ATLL phenotypes. In T-cell tumors occurring in HTLV-1 carriers, the possibility of ATLL should not be eliminated even when the tumor exhibits an atypical phenotype, and the confirmation of HTLV-1 in the tissue is recommended.

Misdiagnosis of angioimmunoblastic T‑cell lymphoma: A case report

Angioimmunoblastic T-cell lymphoma (AITL) is a specific subtype of peripheral T-cell lymphoma that is challenging to diagnose due to the lack of specific pathological characteristics. This report describes the case of a 56-year-old man with Hodgkin lymphoma in whom the gene rearrangement results were positive for TCRβDB+Jβ1/2. Pathological and immunochemical examinations revealed a diagnosis of lymphoma that was a composite of AITL and focal classical Hodgkin lymphoma. Unfortunately, he died soon after the correct diagnosis was made. This case shows that a combination of immunohistochemistry and gene rearrangement analysis can increase the diagnostic accuracy for AITL. A review of the literature on the misdiagnosis of AITL indicates that this disease progresses rapidly with a high mortality rate. Our experience, in this case, highlights the need for early diagnosis.

Current Concepts in Nodal Peripheral T-Cell Lymphomas

This review summarizes the current understanding of mature T-cell neoplasms predominantly involving lymph nodes, including ALK-positive and ALK-negative anaplastic large cell lymphomas, nodal T-follicular helper cell lymphoma, Epstein-Barr virus-positive nodal T/NK-cell lymphoma, and peripheral T-cell lymphoma (PTCL), not otherwise specified. These PTCLs are clinically, pathologically, and genetically heterogeneous, and the diagnosis is made by a combination of clinical information, morphology, immunophenotype, viral positivity, and genetic abnormalities. This review summarizes the pathologic features of common nodal PTCLs, highlighting updates in the fifth edition of the World Health Organization classification and the 2022 International Consensus Classification.

Follicular Helper T-Cell-derived Nodal Lymphomas: Study of Histomorphologic, Immunophenotypic, Clinical, and RHOA G17V Mutational Profile

The study was designed to review the demographic, clinical, and pathologic characteristics of follicular helper T cells (TFH)-derived nodal PTCL in India including angioimmunoblastic T-cell lymphoma (AITL), peripheral T-cell lymphoma (PTCL) with follicular helper T cell phenotype (P-TFH), and follicular T-cell lymphoma with additional immunohistochemistry (IHC) and RHOAG17V mutational analysis, as well as their impact on survival. This retrospective study included 88 cases of PTCL that were reclassified using IHC for TFH markers (PD1, ICOS, BCL6, and CD10) and dendritic-meshwork markers (CD21, CD23). Cases of TFH cell origin were evaluated for RHOAG17V mutation using Sanger sequencing and amplification-refractory mutation system-polymerase chain reaction (PCR) (validated using cloning and quantitative PCR) with detailed clinicopathologic correlation. Extensive re-evaluation with added IHC panel resulted in a total of 19 cases being reclassified, and the final subtypes were AITL (37 cases, 42%), PTCL-not otherwise specified (44, 50%), P-TFH (6, 7%), and follicular T-cell lymphoma (1, 1%). The presence of at least 2 TFH markers (>20% immunopositivity) determined the TFH origin. AITL patients tended to be male and showed increased presence of B-symptoms and hepatosplenomegaly. Histomorphology revealed that 92% of AITL cases had pattern 3 involvement. Sanger sequencing with conventional PCR did not yield any mutation, while RHOAG17V was detected by amplification-refractory mutation system-PCR in AITL (51%, P =0.027) and P-TFH (17%), which was validated with cloning followed by sequencing. Cases of RHOAG17V-mutant AITL had a worse Eastern Cooperative Oncology Group performance status initially but fared better in terms of overall outcome ( P =0.029). Although not specific for AITL, RHOAG17V mutation shows an association with diagnosis and requires sensitive methods for detection due to low-tumor burden. The mutant status of AITL could have prognostic implications and translational relevance.

Pathologic and molecular insights in nodal T-follicular helper cell lymphomas

T-follicular helper (TFH) cells are one of the T-cell subsets with a critical role in the regulation of germinal center (GC) reactions. TFH cells contribute to the positive selection of GC B-cells and promote plasma cell differentiation and antibody production. TFH cells express a unique phenotype characterized by PD-1^hi, ICOS^hi, CD40L^hi, CD95^hi, CTLA^hi, CCR7^lo, and CXCR5^hi . Three main subtypes of nodal TFH lymphomas have been described: 1) angioimmunoblastic-type, 2) follicular-type, and 3) not otherwise specified (NOS). The diagnosis of these neoplasms can be challenging, and it is rendered based on a combination of clinical, laboratory, histopathologic, immunophenotypic, and molecular findings. The markers most frequently used to identify a TFH immunophenotype in paraffin-embedded tissue sections include PD-1, CXCL13, CXCR5, ICOS, BCL6, and CD10. These neoplasms feature a characteristic and similar, but not identical, mutational landscape with mutations in epigenetic modifiers (TET2, DNMT3A, IDH2), RHOA, and T-cell receptor signaling genes. Here, we briefly review the biology of TFH cells and present a summary of the current pathologic, molecular, and genetic features of nodal lymphomas. We want to highlight the importance of performing a consistent panel of TFH immunostains and mutational studies in TCLs to identify TFH lymphomas.

Classification and diagnostic evaluation of nodal T- and NK-cell lymphomas

Nodal T- and NK-cell lymphomas are among the most frequent T-cell malignancies and most subtypes have aggressive clinical behavior. Evolving understanding of the biology and molecular characteristics of these lymphomas, as well as the development of new precision therapy approaches, underscores the importance of ongoing updates to the classification and diagnostic evaluation of this group of malignancies. Here, we discuss the classification of nodal T- and NK-cell lymphomas based on the 2022 International Consensus Classification of Mature Lymphoid Neoplasms (2022 ICC). Lymphomas of T-follicular helper cell origin are now grouped into a single entity, follicular helper T-cell lymphoma (TFH lymphoma), with three subtypes (angioimmunoblastic-type, follicular-type, and not otherwise specified), reflecting their common cellular origin and shared molecular and clinical characteristics. Classification of anaplastic large cell lymphoma (ALCL) remains essentially unchanged; DUSP22-rearranged cases are now considered a genetic subtype of ALK-negative ALCL. Primary nodal EBV-positive T-/NK-cell lymphoma is introduced as a new provisional entity; these cases were previously considered a variant of peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS). PTCL, NOS remains a diagnosis of exclusion, with evolving molecular data indicating the presence of distinct subgroups, including PTCL-TBX21, PTCL-GATA3, and EBV-negative cytotoxic PTCLs. We also discuss diagnostic strategies to facilitate the 2022 ICC classification among nodal T- and NK-cell lymphomas and the distinction from nodal involvement by extranodal neoplasms.

Clinicopathological findings, prognosis, and Epstein-Barr virus infection in rheumatoid arthritis patients with other iatrogenic immunodeficiency-associated T- and NK-cell lymphoproliferative disorders

BACKGROUND

Other iatrogenic immunodeficiency-associated (OIIA) T- and natural killer (NK)-cell lymphoproliferative disorders (TNK-LPDs) are rare in patients with rheumatoid arthritis (RA).

METHODS

We investigated the clinicopathological characteristics, Epstein-Barr virus (EBV) infection, genetic findings, therapeutic response, and prognostic factors in 21 RA patients with OIIA TNK-LPDs and compared these with those of 39 with OIIA B-cell LPDs (B-LPDs) and 22 with non-OIIA B-LPDs.

RESULTS

Immunohistologically, 11 patients (52%) showed CD4+ T-LPDs, and 7 had a T follicular helper (TFH) phenotype. The other nine patients (43%) showed CD8+ T-LPDs, and the remaining one (5%) had features of CD3+ CD4- CD8- nasal type TNK-cell lymphoma. CD30+, p53+, and CMYC+ atypical lymphocytes were identified in seven (33%), eight (38%), and five (24%) patients, respectively. In situ hybridisation detected EBV-encoded RNA (EBER) + large atypical lymphocytes in five patients (24%). Nine of 17 patients (53%) showed clonal peaks of TCRγ by polymerase chain reaction. Withdrawal of MTX and biologic drugs was effective in 12 patients (57%), and 8 (38%) received chemotherapies. Two patients with TFH+ or EBV+ CD4+ CD30+ large cell peripheral T-cell lymphoma, one with CD8+ systemic anaplastic large cell lymphoma, and two with systemic EBV+ CD8+ T-cell lymphoma of childhood showed a lethal progressive clinical course within 13 months. Moreover, > 500 U/L LDH, large atypical lymphocytes, expression of CD30, p53, and CMYC, and EBER+ atypical lymphocytes were significantly poor prognostic factors for overall survival (p < 0.05). Median interval from RA onset to OIIA TNK-LPDs was 72 months, which was shorter than 166 months in OIIA B-LPDs (p = 0.003). EBV+ atypical and reactive lymphocytes were frequently found in 15 patients with OIIA TNK-LPDs (71%), in 27 with OIIA B-LPDs (69%), and only in 3 with non-OIIA B-LPDs (14%).

CONCLUSIONS

OIIA TNK-LPDs occurred in early phase of RA, compared with OIIA B-LPDs, and occasionally showed a lethal progressive clinical course. Detection of OIIA TNK-LPD patients with poor prognostic factors is necessary. EBV infection in immunosuppressed patients due to persistent RA, MTX, and biologic drugs may play a role in forming the tumour microenvironment and lymphomagenesis of TNK-LPDs.

Classification and challenges in the histopathological diagnosis of peripheral T-cell lymphomas, emphasis on the WHO-HAEM5 updates

Mature T-cell lymphomas represent neoplastic expansions of T-cell lymphocytes with a post-thymic derivation. Most of these tumors feature aggressive clinical behavior and challenging histopathological diagnosis and classification. Novel findings in the genomic landscape of T-cell lymphomas are helping to improve the understanding of the biology and the molecular mechanisms that underly its clinical behavior. The most recent WHO-HAEM5 classification of hematolymphoid tumors introduced novel molecular and histopathological findings that will aid in the diagnostic classification of this group of neoplasms. The current review article summarizes the most relevant diagnostic features of peripheral T-cell lymphomas with an emphasis on the updates that are incorporated at the WHO-HAEM5.

The International Consensus Classification of Mature Lymphoid Neoplasms: a report from the Clinical Advisory Committee

Since the publication of the Revised European-American Classification of Lymphoid Neoplasms in 1994, subsequent updates of the classification of lymphoid neoplasms have been generated through iterative international efforts to achieve broad consensus among hematopathologists, geneticists, molecular scientists, and clinicians. Significant progress has recently been made in the characterization of malignancies of the immune system, with many new insights provided by genomic studies. They have led to this proposal. We have followed the same process that was successfully used for the third and fourth editions of the World Health Organization Classification of Hematologic Neoplasms. The definition, recommended studies, and criteria for the diagnosis of many entities have been extensively refined. Some categories considered provisional have now been upgraded to definite entities. Terminology for some diseases has been revised to adapt nomenclature to the current knowledge of their biology, but these modifications have been restricted to well-justified situations. Major findings from recent genomic studies have impacted the conceptual framework and diagnostic criteria for many disease entities. These changes will have an impact on optimal clinical management. The conclusions of this work are summarized in this report as the proposed International Consensus Classification of mature lymphoid, histiocytic, and dendritic cell tumors.

PD-1 combined with TRBC1 and pan-T cell antibodies for robustly monitoring angioimmunoblastic T-cell lymphoma

Background

The diagnosis of AITL is challenging. It may be delayed or even missed due to critical clinical conditions and its histologic and immunophenotypic overlap with other neoplastic and reactive lymphoid proliferations.

Objective

The key objective is to obtain an efficient diagnosis, sensitive disease monitoring and treatment efficacy assessment of AITL using multiparameter flow cytometry (MFC).

Methods

In total, 167 de novo AITL patients were immunophenotypically profiled using sensitive MFC. We precisely identified the aberrant T-cell populations of AITL and performed an in-depth description of their phenotypic characteristics in comparison with their residual normal CD4+ T cells. A comparison of Programmed death receptor-1 (PD-1) expression was performed among AITL and other T-cell lymphomas.

Results

MFC detected a neoplastic T-cell population in 94.1% (80/85) of tissue, 71.5% (108/151) of bone marrow (BM), 100% (8/8) of peripheral blood (PB) and 78.6% (11/14) of body fluid samples. The most frequent immunophenotypic aberrations included the absence and diminished expression of CD3 (71.25% in tissues, 71.3% in BM, 75% in PB, 81.8% in hydrothorax and ascites specimens), followed by the loss or partial loss of CD7 (71.25% in LN, 67.6% in BM, 50% in PB, 81.8% in hydrothorax and ascites specimens). The immunophenotyping of neoplastic T-cell populations showed a high degree of similarity among different sites of the same patient and they might change over time but were relatively stable. Bright PD-1 expression showed high sensitivity and specificity in differentiating AITL from other T-cell lymphomas. In 14 AITL patients, neoplastic T-cell populations were initially missed by T-cell screening tube but were successfully discovered by bright PD-1 expression.

Conclusion

T-cell screening tube can reliably screen neoplastic T-cell populations in AITL patients with typical immunophenotyping, such as loss of surface CD3 and loss of CD7 with a relatively high ratio. Bright PD-1 expression is essential for identifying aberrant T cells in almost all AITLs. The clonality assessment antibody TRBC1 is efficient for robustly and cheaply assessing T-cell clonality. Using PD-1 and TRBC1 combined with pan-T cell antibodies can make a precise diagnosis of AITL and also sensitively monitor minimal residual disease regardless of the antigenic drift of the neoplastic T cells.

Pathological and Molecular Features of Nodal Peripheral T-Cell Lymphomas

Peripheral T-cell lymphomas (PTCLs) are uncommon neoplasms derived from mature T cells or NK cells. PTCLs comprise numerous disease entities, with over 30 distinct entities listed in the latest WHO classification. They predominantly affect adults and elderly people and usually exhibit an aggressive clinical course with poor prognosis. According to their presentation, PTCLs can be divided into nodal, extranodal or cutaneous, and leukemic types. The most frequent primary sites of PTCLs are lymph nodes, with over half of cases showing nodal presentation. Nodal PTCLs include ALK-positive and ALK-negative anaplastic large cell lymphoma; nodal T-cell lymphoma with T follicular helper cell origin; and PTCL, not otherwise specified. Adult T-cell leukemia/lymphoma also frequently affects lymph nodes. Recent pathological and molecular findings in nodal PTCLs have profoundly advanced the identification of tumor signatures and the refinement of the classification. Therefore, the therapies and pathological diagnosis of nodal PTCLs are continually evolving. This paper aims to provide a summary and update of the pathological and molecular features of nodal PTCLs, which will be helpful for diagnostic practice.

Human Germinal Center-associated Lymphoma (HGAL) Is a Reliable Marker of Normal and Neoplastic Follicular Helper T Cells Including Angioimmunoblastic T-Cell Lymphoma

The diagnosis of angioimmunoblastic T-cell lymphoma (AITL) is complex and requires the demonstration of a T-follicular helper (TFH) phenotype. Immunophenotypic markers that detect the TFH phenotype are highly variable, thereby necessitating the use of 3 to 5 TFH markers to substantiate a TFH phenotype. We tested the utility of germinal center markers human germinal center-associated lymphoma (HGAL) and LIM-domain only 2 (LMO2) in detecting a TFH phenotype. We compared their staining to that of 6 TFH markers in current use, PD-1, ICOS, CXCL13, SAP, CD10, and BCL6, in a cohort of 23 AITL. Our results show that although both markers can detect a TFH phenotype, HGAL was superior to LMO2 in the percent of cells stained and the intensity of staining, 2 variables used to generate H-scores. Using H-scores as the metric, HGAL was most comparable to BCL6 among the currently used TFH markers and was more sensitive than CXCL13, SAP, CD10, and LMO2. PD-1 and ICOS emerged as the most robust of the 8 markers tested in this study in detecting a TFH phenotype. We conclude that HGAL is a reliable marker of TFH cells and can aid in the diagnosis of lymphomas of TFH derivation, particularly in the recognition of early patterns of AITL.

Large cell morphology, CMYC+ tumour cells, and PD-1+ tumour cell/intense PD-L1+ cell reactions are important prognostic factors in nodal peripheral T-cell lymphomas with T follicular helper markers

BACKGROUND

The clinicopathological characteristics and prognostic factors in nodal peripheral T-cell lymphomas (PTCLs) with two or more T follicular helper markers (TFH+) are not adequately investigated.

METHODS

Immunohistologically, we selected 22 patients with TFH+ lymphoma (PTCL-TFH) in 47 of PTCL-not otherwise specified (NOS), and subclassified into large and small cell groups. We compared the two groups with 39 angioimmunoblastic T-cell lymphoma (AITL) and seven follicular T-cell lymphoma (F-TCL) patients. Prognostic factors were analysed by overall survival in patients with three types of TFH+ PTCLs.

RESULTS

Thirteen large cell and nine small cell PTCL-TFH patients had more than two TFH markers including programmed cell death-1 (PD-1). Large cell PTCL-TFH showed frequent CMYC expression in 10 patients (77%), and four of 11 large cell group (36%) had somatic RHOA G17V gene mutation by Sanger sequencing. Large cell PTCL-TFH patients showed significantly worse prognosis than those of the small cell group, AITL, and F-TCL (p < 0.05). In TFH+ PTCLs, CMYC+ tumour cells, and combined PD-1 ligand 1 (PD-L1) + tumour cells and intense reaction of PD-L1+ non-neoplastic cells (high PD-L1+ cell group) were significantly poor prognostic factors (p < 0.05). Combinations of CMYC+ or PD-1+ tumour cells and high PD-L1+ cell group indicated significantly poor prognosis (p < 0.01).

CONCLUSION

Large cell PTCL-TFH indicated poor prognosis in TFH+ PTCLs. These data suggested that CMYC+ tumour cells and intense PD-L1+ cell reaction influenced tumour cell progression in TFH+ PTCLs, and PD-1+ tumour cell/intense PD-L1+ cell reactions may play a role in immune evasion.

SOHO State of the Art Updates and Next Questions: Pathology and Pathogenesis of Nodal Peripheral T-Cell Lymphomas

Peripheral T-cell lymphomas (PTCLs) are a heterogeneous and often clinically aggressive group of neoplasms derived from mature post-thymic T-lymphocytes. These neoplasms are rare and usually diagnostically challenging. Our understanding of the pathogenesis of PTCL is increasing and this improved knowledge is leading us to better molecular characterization, more objective and accurate diagnostic criteria, more effective risk assessment, and potentially better treatments. The focus of this paper is to present a brief overview of the current pathology criteria and molecular and genetic features of nodal peripheral T-cell lymphomas focusing on distinct genetically and molecularly defined subgroups that are being recognized within each major nodal PTCL category. It is expected that the molecular stratification will improve the diagnosis and will provide novel therapeutic opportunities (biomarker-driven and targeted therapies) that might benefit and change the outcomes of patients with these neoplasms.

How I Diagnose Angioimmunoblastic T-Cell Lymphoma

OBJECTIVES

Angioimmunoblastic T-cell lymphoma (AITL) is a subtype of peripheral T-cell lymphoma derived from T-follicular helper cells. For pathologists, diagnosing AITL may be challenging due to its wide clinical and histopathologic spectrum, which can mimic a variety of reactive and neoplastic processes.

METHODS

We summarize and discuss the clinicopathologic features of AITL, emphasizing diagnostic tools available to the practicing pathologist. Common diagnostic dilemmas are discussed.

RESULTS

AITL exhibits various histologic patterns and is often associated with a prominent microenvironment that can obscure the neoplastic cells. Atypical B-cell proliferations, which can take a number of forms, are common in AITL, and clonal B-cell expansion can be seen. The atypical B cells can closely resemble Hodgkin/Reed-Sternberg cells, leading to misdiagnosis as classic Hodgkin lymphoma. Molecular studies have revealed recurrent genetic alterations, which can aid in differential diagnosis, particularly in problematic cases.

CONCLUSIONS

Given the complex diagnostic challenges in AITL, an integrated approach, incorporating clinical, morphologic, immunophenotypic, and molecular findings, is helpful to reach an accurate diagnosis.

New developments in non-Hodgkin lymphoid malignancies

The revised fourth edition of the World Health Organization (WHO) Classification of Tumours of Haematopoietic and Lymphoid Tissues (2017) reflects significant advances in understanding the biology, genetic basis and behaviour of haematopoietic neoplasms. This review focuses on some of the major changes in B-cell and T-cell non-Hodgkin lymphomas in the 2017 WHO and includes more recent updates. The 2017 WHO saw a shift towards conservatism in the classification of precursor lesions of small B-cell lymphomas such as monoclonal B-cell lymphocytosis, in situ follicular and in situ mantle cell neoplasms. With more widespread use of next generation sequencing (NGS), special entities within follicular lymphoma and mantle cell lymphoma were recognised with recurrent genetic aberrations and unique clinicopathological features. The diagnostic workup of lymphoplasmacytic lymphoma and hairy cell leukaemia has been refined with the discovery of MYD88 L265P and BRAF V600E mutations, respectively, in these entities. Recommendations in the immunohistochemical evaluation of diffuse large B-cell lymphoma include determining cell of origin and expression of MYC and BCL2, so called 'double-expressor' phenotype. EBV-positive large B-cell lymphoma of the elderly has been renamed to recognise its occurrence amongst a wider age group. EBV-positive mucocutaneous ulcer is a newly recognised entity with indolent clinical behaviour that occurs in the setting of immunosuppression. Two lymphomas with recurrent genetic aberrations are newly included provisional entities: Burkitt-like lymphoma with 11q aberration and large B-cell lymphoma with IRF4 rearrangement. Aggressive B-cell lymphomas with MYC, BCL2 and/or BCL6 rearrangements, so called 'double-hit/triple-hit' lymphomas are now a distinct entity. Much progress has been made in understanding intestinal T-cell lymphomas. Enteropathy-associated T-cell lymphoma, type II, is now known to not be associated with coeliac disease and is hence renamed monomorphic epitheliotropic T-cell lymphoma. An indolent clonal T-cell lymphoproliferative disorder of the GI tract is a newly included provisional entity. Angioimmunoblastic T-cell lymphoma and nodal T-cell lymphomas with T-follicular helper phenotype are included in a single broad category, emphasising their shared genetic and phenotypic features. Anaplastic large cell lymphoma, ALK- is upgraded to a definitive entity with subsets carrying recurrent rearrangements in DUSP22 or TP63. Breast implant-associated anaplastic large cell lymphoma is a new provisional entity with indolent behaviour. Finally, cutaneous T-cell proliferations include a new provisional entity, primary cutaneous acral CD8-positive T-cell lymphoma, and reclassification of primary small/medium CD4-positive T-cell lymphoma as lymphoproliferative disorder.

Clinicopathological characterization of follicular helper T-cell-derived peripheral T-cell lymphoma involving Waldeyer's ring

Follicular helper T-cell-derived peripheral T-cell lymphoma (TFH-derived PTCL) initially present in the Waldeyer's ring is a rare condition with a challenging diagnosis. This study aimed to evaluate the clinicopathological characteristics and diagnosis of Waldeyer's ring TFH-derived PTCL and raise awareness of this type of lymphoma. A series of 13 cases of Waldeyer's ring TFH-derived PTCL were retrospectively analyzed. Clinically, most patients presented with localized manifestations, such as painless cervical lymphadenopathy (7/13), pharyngalgia (6/13), and nasal obstruction (3/13), and systemic symptoms were uncommon. Macroscopically, plump mass (9/13) and nodular lesions (3/13) covered with intact and tense mucosa were the main findings on fiberoptic laryngoscopy examination. Pathologically, diffuse infiltration with atypical lymphocytes in the lamina propria (10/13) was the most common growth pattern. Clear cells (9/13) and vascular proliferation (11/13) within a polymorphic inflammatory background (11/13) were frequently observed. All cases expressed at least two TFH markers: PD-1 in 92.3% (12/13), BCL6 in 69.2% (9/13), CXCL13 in 53.8% (7/13), and CD10 in 46% (6/13). Targeted next-generation sequencing analysis identified frequent mutations, including TET2 (10/11), RHOA (6/11), DNMT3A (3/11), and IDH2 (2/11). The overall survival rate at 2 years was 35.5%, and survival analysis revealed that patients with localized disease showed better overall survival (P = 0.022). In conclusion, careful morphological observation combined with immunohistochemistry and molecular analysis would help in diagnosis of TFH-derived PTCL involving the Waldeyer's ring, which is a rare condition that frequently presents with atypical clinical manifestations.

Reactive Eosinophil Proliferations in Tissue and the Lymphocytic Variant of Hypereosinophilic Syndrome

OBJECTIVES

The 2019 Society for Hematopathology and European Association for Haematopathology Workshop reviewed the spectrum of neoplastic, nonneoplastic, and borderline entities associated with reactive eosinophilia in tissue.

METHODS

The workshop panel reviewed 46 cases covered in 2 workshop sessions.

RESULTS

The 46 cases were presented with their consensus diagnoses during the workshop. Reactive eosinophilia in lymph nodes and other tissues may be accompanied by or be distinct from peripheral blood eosinophilia. Reactive etiologies included inflammatory disorders such as Kimura disease and IgG4-related disease, which may show overlapping pathologic features and reactions to infectious agents and hypersensitivity (covered in a separate review). Hodgkin, T-cell, and B-cell lymphomas and histiocytic neoplasms can result in reactive eosinophilia. The spectrum of these diseases is discussed and illustrated through representative cases.

CONCLUSIONS

Reactive eosinophilia in lymph nodes and tissues may be related to both nonneoplastic and neoplastic lymphoid proliferations and histiocytic and nonhematolymphoid processes. Understanding the differential diagnosis of reactive eosinophilia and the potential for overlapping clinical and pathologic findings is critical in reaching the correct diagnosis so that patients can be treated appropriately.

In Situ Characterization of Follicular Helper CD4 T Cells Using Multiplexed Imaging

Follicular helper CD4 T (Tfh) cells play an essential role in the formation of germinal centers (GCs), where mature B cells proliferate, differentiate, and provide long-term protective humoral responses. Despite the extensive phenotypic characterization and identification of human Tfh cell subsets, their spatial positioning at tissue level is not well understood. Here, we describe a quantitative multiplexed immunofluorescence approach allowing for the comprehensive in situ characterization of Tfh cells in human tonsils and lymph nodes (LNs) from individuals with angioimmunoblastic T-cell lymphoma (AITL). We have developed eight multiplexed panels comprising a spectrum of Tfh cell markers, like PD-1, CXCR5, and ICOS, along with transcription factors (Bcl6, Tbet, GATA3), to assess their expression, frequencies, spatial distribution and co-localization in a quantitative manner. Combined analysis of relevant markers revealed the presence of several Tfh cell subsets at tissue level based on the differential expression of surface receptors, nuclear factors as well as their distinct localization within the follicular areas. Interestingly, we found a considerable amount of tonsillar Tfh cells expressing high levels of the Th2 regulator GATA3. The co-expression of GATA3, CXCR5, and BCL6, points to an important role of GATA3 for the generation of effector human Tfh cells. Furthermore, our data revealed significantly different Tfh cell profile signatures between health and disease. Therefore, our imaging platform generates meaningful information for the in situ characterization of human Tfh cells and could provide the base for future studies aiming to a comprehensive understanding of Tfh cell tissue heterogeneity.

The first reported case of primary extranodal counterpart of follicular T-cell lymphoma of submandibular gland

This is the first reported case of follicular T-cell lymphoma (FTCL) that primarily developed in the extranodal site of the right submandibular gland. An 86-year-old man was detected with a right cervical mass suspected to be malignant lymphoma during his physical examination. Imaging studies revealed that the mass was a submandibular gland tumor. The tumor was excised for diagnosis and treatment. Pathologically, the tumor was composed of densely aggregated lymphocytes with a follicular growth pattern. The immunohistochemical investigation showed that the lymphoma cells expressed CD3, CD4, programmed cell death protein 1, BCL6, chemokine (C-X-C motif) ligand 13, and BCL2. Staining of the follicular dendritic cell revealed its meshwork structure limited in the germinal center. Monoclonal rearrangement of the T-cell receptor was detected using polymerase chain reaction. These findings are consistent with the characteristics of FTCL. Here, we describe the first reported case of extranodal counterpart of FTCL of the submandibular gland. Accumulation and investigation of such extranodal cases is essential.

American Registry of Pathology Expert Opinions: Recommendations for the diagnostic workup of mature T cell neoplasms

The diagnosis of T-cell lymphomas is highly challenging and requires an integrated approach in which clinical, morphologic, immunophenotypic and molecular data are incorporated into the diagnosis. Under the auspices of the American Registry of Pathology, the authors met to discuss this topic with the goal to provide practical and useful recommendations for pathologists when evaluating T-cell lymphomas. In this review, we discuss the diagnostic findings and workup for the various types of nodal T-cell lymphoma including anaplastic large cell lymphoma, nodal peripheral T-cell lymphoma not otherwise specified (PTCL-NOS), and PTCL with a T follicular helper (TFH) phenotype. We review clinicopathologic and immunophenotypic features (including flow cytometry panels) helpful in the differential diagnosis of mature T-cell lymphomas presenting in the peripheral blood and bone marrow, and we discuss some of the more common extranodal-based T-cell lymphomas including extranodal natural killer/T-cell lymphoma of nasal and non-nasal type, gamma delta T cell lymphomas, and aggressive and indolent T- and NK-lymphoproliferative disorders involving the gastrointestinal tract. Mycosis fungoides and most other cutaneous T-cell lymphomas are not the focus of this review, although the differential diagnosis of Sezary syndrome from mycosis fungoides is covered. We do not intend for these recommendations to be anything other than suggestions that will hopefully spur on additional discussion, and perhaps eventually evolve into a consensus approach for the workup of T-cell lymphomas.

How I Diagnose Primary Cutaneous Marginal Zone Lymphoma

OBJECTIVES

Primary cutaneous marginal zone lymphoma (PCMZL) is 1 of the 3 major subtypes of primary cutaneous B-cell lymphoma. The diagnosis of PCMZL may be challenging, as the differential diagnosis includes benign cutaneous lymphoproliferations as well as other primary or secondary cutaneous B-cell or T-cell lymphomas. This review describes our approach to the diagnosis of PCMZL.

METHODS

Two cases are presented that illustrate how we diagnose each of the 2 subtypes of PCMZL. The clinicopathologic features of PCMZL and the ways in which these cases can be distinguished from both benign and other neoplastic entities are emphasized.

RESULTS

A definitive diagnosis of PCMZL requires the incorporation of histologic and immunophenotypic features, molecular genetic studies in some cases, and just as importantly, clinical findings. Emerging data suggest that the heavy chain class-switched cases may be more like a clonal chronic lymphoproliferative disorder.

CONCLUSIONS

The 2 subtypes of PCMZL create different diagnostic challenges and require the use of a multiparameter approach. Although very indolent, it is important to distinguish PCMZLs from reactive proliferations, because they frequently recur and may require antineoplastic therapies. It is also critical to distinguish PCMZLs from other B- or T-cell lymphomas so that patients are properly evaluated and not overtreated.

A suggested immunohistochemical algorithm for the classification of T-cell lymphomas involving lymph nodes

T-cell lymphomas are a heterogeneous group of neoplasms derived from mature T lymphocytes. These neoplasms are uncommon and usually diagnostically challenging. The focus of this article is to suggest an immunohistochemistry-based, practical approach to assist in the diagnosis of nodal T-cell lymphomas. These neoplasms fall into two major groups: those with many CD30+ tumor cells (group A) and neoplasms that are negative or show only partial expression of CD30 (group B). The differential diagnosis of group A neoplasms mainly includes ALK+ anaplastic large-cell lymphoma (ALCL), ALK-negative ALCL, mycosis fungoides with CD30+ large-cell transformation, adult T-cell leukemia/lymphoma, extranodal T-cell lymphomas involving lymph nodes (usually regional), and peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS). Group B neoplasms also include two groups based on the presence or absence of T follicular helper (TFH) markers. Those neoplasms expressing at least 2 TFH markers include angioimmunoblastic T-cell lymphoma, nodal PTCL with a TFH phenotype, and follicular T-cell lymphoma. Neoplasms expressing ≤1 TFH marker can be further subdivided based on the expression of CD8 and cytotoxic markers and mainly include PTCL-NOS and a series of unusual subsets including primary Epstein-Barr virus-positive nodal natural killer/T-cell lymphoma, PTCL-NOS with a cytotoxic immunophenotype, and γ/δ T-cell lymphomas. Using this algorithmic approach, we suggest that the pathologist can establish a diagnosis for most nodal T-cell lymphomas encountered in daily practice.

Update on peripheral T-cell lymphomas with T-helper phenotype: Are there too many subtypes?

Follicular helper T (T_FH) cells are the providers of T-cell help to B-cells in the development of germinal centers and for the generation of most class-switched antibodies. The markers most commonly associated with T_FH activity are IL21, IL4, CD40L, BCL6, SAP, CXCR5/CXCL13, and ICOS. T-cell lymphoma genomic studies have shown that different T-cell lymphoma types express signatures typical for T_FH cells, this including angioimmunoblastic T-cell lymphoma (AITL), a related condition termed peripheral T-cell lymphoma with T_FH phenotype and primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder. Angioimmunoblastic T-cell lymphoma is a well-established entity, a clinically aggressive disease with a survival of 30% OS after 5 years. Molecular and clinical studies have confirmed this as a well-established clinicopathological entity with relatively specific gene mutations, including mutations found in hematopoietic precursor cells and others. Peripheral T-cell lymphoma with T_FH phenotype is an associated disorder with histology of PTCL but a T_FH phenotype, as defined by the expression of 2-3 immunohistochemical markers. Molecular studies on this entity are showing a partial overlap with AITL. Primary cutaneous CD4+ small/medium lymphoproliferative disorder is an entirely different process that takes place in the skin, showing frank cytologic atypia, monoclonal TCR rearrangement and T_FH phenotype in the context of a clinically benign lesion. Here we review the main clinical, molecular and diagnostic features of these three lymphoproliferative processes.