The current role of clinical flow cytometry in the evaluation of mature B-cell neoplasms

Posterior Uveitis in Ocular-Involving Chronic Lymphocytic Leukemia and the Utility of Negative MYD88 L265P Testing in the Diagnosis

Introduction

The aim of this study was to investigate if a negative test result for MYD88 L265P mutation, associated with vitreoretinal lymphoma (VRL) and primary CNS lymphoma, in liquid biopsies from intraocular fluids can be a useful adjuvant test to diagnose chronic lymphocytic leukemia in clinically challenging cases.

Case Presentations

We selected patients with a past medical history or examinations findings suspicious for intraocular lymphoma. We evaluated both vitreous and aqueous humor-derived (AHD) MYD88 L265P mutation from patients that had suspected intraocular lymphoma that warranted a liquid biopsy procedure. Gold-standard cytopathology, flow cytometry, and gene rearrangement studies were also performed. All 4 patients had negative AHD MYD88 L265P mutation testing. Gold-standard testing (cytology) either showed paucicellular specimens (1/4) or specimens with high background inflammation (3/4). One case showed a rare B-cell clonal population (CD5+, Kappa-restricted by flow cytometry), but this was not sufficient to make any definitive diagnosis. All patients were subsequently initiated on systemic therapy and had improvement in their disease burden.

Conclusions

Negative AHD MYD88 L265P mutation testing can serve as an adjuvant molecular test to diagnose difficult cases of intraocular CLL.

Recommendations for using artificial intelligence in clinical flow cytometry

Flow cytometry is a key clinical tool in the diagnosis of many hematologic malignancies and traditionally requires close inspection of digital data by hematopathologists with expert domain knowledge. Advances in artificial intelligence (AI) are transferable to flow cytometry and have the potential to improve efficiency and prioritization of cases, reduce errors, and highlight fundamental, previously unrecognized associations with underlying biological processes. As a multidisciplinary group of stakeholders, we review a range of critical considerations for appropriately applying AI to clinical flow cytometry, including use case identification, low and high risk use cases, validation, revalidation, computational considerations, and the present regulatory frameworks surrounding AI in clinical medicine. In particular, we provide practical guidance for the development, implementation, and suggestions for potential regulation of AI-based methods in the clinical flow cytometry laboratory. We expect these recommendations to be a helpful initial framework of reference, which will also require additional updates as the field matures.

Flow cytometry quantification of tumor-infiltrating lymphocytes to predict the survival of patients with diffuse large B-cell lymphoma

Introduction

Our previous studies have demonstrated that tumor-infiltrating lymphocytes (TILs), including normal B cells, T cells, and natural killer (NK) cells, in diffuse large B-cell lymphoma (DLBCL) have a significantly favorable impact on the clinical outcomes of patients treated with standard chemoimmunotherapy. In this study, to gain a full overview of the tumor immune microenvironment (TIME), we assembled a flow cytometry cohort of 102 patients diagnosed with DLBCL at the Duke University Medical Center.

Methods

We collected diagnostic flow cytometry data, including the proportion of T cells, abnormal B cells, normal B cells, plasma cells, NK cells, monocytes, and granulocytes in fresh biopsy tissues at clinical presentation, and analyzed the correlations with patient survival and between different cell populations.

Results

We found that low T cell percentages in all viable cells and low ratios of T cells to abnormal B cells correlated with significantly poorer survival, whereas higher percentages of normal B cells among total B cells (or high ratios of normal B cells to abnormal B cells) and high percentages of NK cells among all viable cells correlated with significantly better survival in patients with DLBCL. After excluding a small number of patients with low T cell percentages, the normal B cell percentage among all B cells, but not T cell percentage among all cells, continued to show a remarkable prognostic effect. Data showed significant positive correlations between T cells and normal B cells, and between granulocytes and monocytes. Furthermore, we constructed a prognostic model based on clinical and flow cytometry factors, which divided the DLBCL cohort into two equal groups with remarkable differences in patient survival and treatment response.

Summary

TILs, including normal B cells, T cells, and NK cells, are associated with favorable clinical outcomes in DLBCL, and flow cytometry capable of quantifying the TIME may have additional clinical utility for prognostication.

Analysis of False-negative Findings of the Incomparable Accuracy and Swiftness of Flow Cytometric Diagnosis of Primary Central Nervous System Lymphoma

Primary central nervous system lymphoma (PCNSL), a relatively rare brain tumor, bears a dire prognosis. On occasion, the rapid progression of the tumor makes immediate diagnosis and initiation of therapy imperative. To achieve swift diagnosis, we adopt flow cytometry (FCM) in addition to conventional histopathology. This study aimed to reveal the utility of FCM diagnosis for PCNSL and the cause of false-negative results of FCM diagnosis. We investigated 33 patients with suspected PCNSL on neuroradiological findings and received both FCM and histological diagnosis. The patients' electronic medical records were investigated, and histological findings, results of FCM, and other clinical data were evaluated. Overall, 27 patients (14 males and 13 females) were diagnosed with PCNSL by histological confirmation. The median age at diagnosis was 68 years. FCM analysis showed lymphoma pattern in 24 cases; however, FCM results did not show lymphoma pattern (sensitivity: 88.9%, specificity: 100%) in the other three lymphoma cases (FCM discordant: FCM-D) and six nonlymphomatous tumor cases. Analysis of FCM-D cases showed the infiltration of T lymphocytes or astrocytes into the tumor tissue, indicating tumor microenvironmental reaction; it is assumed that these reactions deceived FCM diagnosis. The survival of FCM-D patients was superior to FCM concordant counterpart, although the difference was not significant (p = 0.459). The diagnosis of PCNSL by FCM is rapid and highly reliable. Some FCM-D cases are PCNSLs with strong tumor microenvironmental reactions.

Machine learning models-based on integration of next-generation sequencing testing and tumor cell sizes improve subtype classification of mature B-cell neoplasms

Background

Next-generation sequencing (NGS) panels for mature B-cell neoplasms (MBNs) are widely applied clinically but have yet to be routinely used in a manner that is suitable for subtype differential diagnosis. This study retrospectively investigated newly diagnosed cases of MBNs from our laboratory to investigate mutation landscapes in Chinese patients with MBNs and to combine mutational information and machine learning (ML) into clinical applications for MBNs, especially for subtype classification.

Methods

Samples from the Catalogue Of Somatic Mutations In Cancer (COSMIC) database were collected for ML model construction and cases from our laboratory were used for ML model validation. Five repeats of 10-fold cross-validation Random Forest algorithm was used for ML model construction. Mutation detection was performed by NGS and tumor cell size was confirmed by cell morphology and/or flow cytometry in our laboratory.

Results

Totally 849 newly diagnosed MBN cases from our laboratory were retrospectively identified and included in mutational landscape analyses. Patterns of gene mutations in a variety of MBN subtypes were found, important to investigate tumorigenesis in MBNs. A long list of novel mutations was revealed, valuable to both functional studies and clinical applications. By combining gene mutation information revealed by NGS and ML, we established ML models that provide valuable information for MBN subtype classification. In total, 8895 cases of 8 subtypes of MBNs in the COSMIC database were collected and utilized for ML model construction, and the models were validated on the 849 MBN cases from our laboratory. A series of ML models was constructed in this study, and the most efficient model, with an accuracy of 0.87, was based on integration of NGS testing and tumor cell sizes.

Conclusions

The ML models were of great significance in the differential diagnosis of all cases and different MBN subtypes. Additionally, using NGS results to assist in subtype classification of MBNs by method of ML has positive clinical potential.

MALT lymphoma of the sublingual gland: A case report with current overview of diagnostic and therapeutic strategies

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) is a low-grade B-cell lymphoma. MALT lymphomas involving the sublingual gland are extremely rare. Herein, we report a case of MALT lymphoma of the sublingual gland. Additionally, we discuss challenging diagnostic aspects as well as current treatment strategies.

Follicular lymphoma: updates for pathologists

Follicular lymphoma (FL) is the most common indolent B-cell lymphoma and originates from germinal center B-cells (centrocytes and centroblasts) of the lymphoid follicle. Tumorigenesis is believed to initiate early in precursor B-cells in the bone marrow (BM) that acquire the t(14;18)(q32;q21). These cells later migrate to lymph nodes to continue their maturation through the germinal center reaction, at which time they acquire additional genetic and epigeneticabnormalities that promote lymphomagenesis. FLs are heterogeneous in terms of their clinicopathologic features. Most FLs are indolent and clinically characterized by peripheral lymphadenopathy with involvement of the spleen, BM, and peripheral blood in a substantial subset of patients, sometimes accompanied by constitutional symptoms and laboratory abnormalities. Diagnosis is established by the histopathologic identification of a B-cell proliferation usually distributed in an at least partially follicular pattern, typically, but not always, in a lymph node biopsy. The B-cell proliferation is biologically of germinal center cell origin, thus shows an expression of germinal center-associated antigens as detected by immunophenotyping. Although many cases of FLs are typical and histopathologic features are straightforward, the biologic and histopathologic variability of FL is wide, and an accurate diagnosis of FL over this disease spectrum requires knowledge of morphologic variants that can mimic other lymphomas, and rarely non-hematologic malignancies, clinically unique variants, and pitfalls in the interpretation of ancillary studies. The overall survival for most patients is prolonged, but relapses are frequent. The treatment landscape in FL now includes the application of immunotherapy and targeted therapy in addition to chemotherapy.

Clinicopathological analysis of diffuse large B-cell lymphoma lacking surface immunoglobulin light chain restriction on flow cytometry

Although diffuse large B-cell lymphoma (DLBCL) occasionally lacks surface immunoglobulin light chain restriction (iLCR) on flow cytometry (FCM), little evidence is available for iLCR-negative DLBCL. We retrospectively compared clinicopathological features of iLCR-positive and iLCR-negative DLBCL diagnosed at our institute between April 2007 and March 2018. iLCR-positive was defined as a κ/λ ratio less than 0.5 or greater than 3 in the gated population on dual-color FCM, and iLCR-negative as other values. Of 81 DLBCL cases with available immunophenotyping by FCM, 63 iLCR-positive DLBCL (78%) and 18 iLCR-negative DLBCL (22%) cases were identified. Survival outcomes of patients with iLCR-negative DLBCL were comparable with those of patients with iLCR-positive DLBCL. Pathological analysis revealed no significant difference except for the lower expression of BCL6 in iLCR-negative DLBCL (12.5% vs 65.5%, p < 0.001), although there was a slightly higher frequency of necrosis (47.1% vs 20.7%, p = 0.058) and lower expression of CD10 (11.8% vs 35.0%, p = 0.078) in iLCR-negative DLBCL than in iLCR-positive DLBCL. The underlying mechanism remains unclear; however, low expression of germinal center markers and tumor necrosis may be associated with the loss of iLCR in DLBCL.

Promising Immunotherapeutic Modalities for B-Cell Lymphoproliferative Disorders

Over the last few years, treatment principles have been changed towards more targeted therapy for many B-cell lymphoma subtypes and in chronic lymphocytic leukemia (CLL). Immunotherapeutic modalities, namely monoclonal antibodies (mAbs), bispecific antibodies (bsAbs), antibody-drug conjugates (ADCs), and chimeric antigen receptor T (CAR-T) cell therapy, commonly use B-cell-associated antigens (CD19, CD20, CD22, and CD79b) as one of their targets. T-cell engagers (TCEs), a subclass of bsAbs, work on a similar mechanism as CAR-T cell therapy without the need of previous T-cell manipulation. Currently, several anti-CD20xCD3 TCEs have demonstrated promising efficacy across different lymphoma subtypes with slightly better outcomes in the indolent subset. Anti-CD19xCD3 TCEs are being developed as well but only blinatumomab has been evaluated in clinical trials yet. The results are not so impressive as those with anti-CD19 CAR-T cell therapy. Antibody-drug conjugates targeting different B-cell antigens (CD30, CD79b, CD19) seem to be effective in combination with mAbs, standard chemoimmunotherapy, or immune checkpoint inhibitors. Further investigation will show whether immunotherapy alone or in combinatory regimens has potential to replace chemotherapeutic agents from the first line treatment.

Application of CD54 in diagnosing bone marrow involvement by using flow cytometry in patients with diffuse large B-cell lymphoma

Background

Flow cytometry plays a key role in detecting bone marrow (BM) involvement in patients with diffuse large B-cell lymphoma (DLBCL). To improve its detection sensitivity, we need to explore novel markers. In this study, we detected the expression CD54 on lymphoma cells in BM specimens from DLBCL patients and clarified its diagnostic significance in BM involvement by DLBCL.

Methods

We collected BM specimens from 76 patients with DLBCL (germinal center B-cell (GCB) = 25, non-GCB = 51) and 10 control patients without lymphoma. We detected and compared the expression of CD54 on lymphoma cells and normal mature B cells by using 10-color panels.

Results

Normal plasma cells expressed a higher level of CD54 as compared with hematogones (p < 0.05) and normal mature B cells (p < 0.05). Among 76 patients, 23 of them (GCB = 12, non-GCB = 11) had BM involvement. Lymphoma B cells from 12 cases (GBC = 4, non-GCB = 8) expressed a higher level of CD54 compared to normal mature B cells (p < 0.05). Additionally, lymphoma cells of the non-GCB subtype frequently expressed a higher level of CD54 in comparison to the GCB subtype (p < 0.05). And the high expression of CD54 was not related to plasmacytoid differentiation.

Conclusion

Aberrant expression of CD54 on lymphoma cells is frequently seen in patients’ BM specimens involved by DLBCL, especially in the non-GCB subtype. CD54 could be used as a new marker to gate on lymphoma cells and improve the detection sensitivity of BM involvement in patients with DLBCL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08753-0.

Analysis of clonality in cutaneous B-cell lymphoma and B-cell pseudolymphoma using skin flow cytometry: Comparison of immunophenotyping and gene rearrangement studies

To identify clonal neoplastic cells in skin affected by B-cell lymphoma using skin flow cytometry (FCM) techniques, we investigated light-chain restriction using skin FCM with clonality assessed by polymerase chain reaction and light-chain restriction by in situ hybridization (ISH). We retrospectively analyzed 16 cases of B-cell lymphoma with cutaneous involvement: primary cutaneous diffuse large B-cell lymphoma, leg type (pcDLBCL-LT) (n = 7), DLBCL-not otherwise specified (DLBCL-NOS) (n = 6), primary cutaneous follicle center lymphoma (pcFCL) (n = 1), and follicular lymphoma (n = 2), as well as cutaneous B-cell pseudolymphoma (n = 9). Results of skin FCM light-chain restriction analyses were compared with immunoglobulin H (IgH) gene rearrangement and κ/λ ISH findings. Skin FCM detected light-chain restriction in 11 of 14 B-cell lymphoma patients but none of the B-cell pseudolymphoma patients. The sensitivity of skin FCM for distinguishing B-cell lymphoma and B-cell pseudolymphoma was 79%, and the specificity was 100%. Eleven of 13 B-cell lymphoma patients exhibited gene rearrangement (sensitivity 85%), whereas six of seven pseudolymphoma patients were negative (specificity 86%). ISH was positive in three of 16 B-cell lymphoma cases (sensitivity 19%) but none of the B-cell pseudolymphoma cases (specificity 100%). ISH sensitivity was 29% for pcDLBCL-LT, 17% for DLBCL-NOS, and 0% for pcFCL and follicular lymphoma. Skin FCM therefore appears to be more sensitive than ISH in detecting light-chain restriction in DLBCL and follicular lymphoma, and as sensitive as IgH gene rearrangement analysis in detecting clonality. Skin FCM is thus a promising diagnostic tool for identifying monoclonal neoplastic B-cell populations.

A new score including CD43 and CD180: Increased diagnostic value for atypical chronic lymphocytic leukemia

Moreau score has been used to differentiate chronic lymphocytic leukemia (CLL) from other mature B‐cell neoplasms. However, it showed limitations in Asian patients. Therefore, we conducted a new score system replacing CD5 and CD23 with CD43 and CD180 to evaluate its diagnostic value of CLL. 237 untreated samples diagnosed with mature B‐cell neoplasms were collected and were randomly divided into an exploratory and a validation cohort by a 2:1 ratio. The expression of CD5, CD19, CD20, CD23, CD43, CD79b, CD180, CD200, FMC7, and surface immunoglobulin (SmIg) were analyzed among all the samples. A proposed score was developed based on the logistic regression model. The sensitivity and specificity of the proposed score were calculated by ROC curves. CD43/CD180, CD200, FMC7, and CD79b were included in our new CLL score, which showed a sensitivity of 91.8% and a specificity of 83.1%. These results were confirmed in a validation cohort with a sensitivity of 90.5% (p = 0.808) and a specificity of 79.5% (p = 0.639). In CD5 negative or CD23 negative CLL group, the new CLL score displayed improved sensitivity of 79.4% compared to Moreau score and CLLflow score (41.2% and 47.1%, respectively). In atypical CLL group, the new CLL score showed improved sensitivity of 84.2% compared to Moreau score and CLLflow score (61.4% and 64.9%, respectively). This proposed atypical CLL score helped to offer an accurate differentiation of CLL from non‐CLL together with morphological and molecular methods, particularly in Chinese patients with atypical immunophenotype.

VS38 staining contributes to a novel gating strategy in flow cytometry for small B cell lymphoma, especially in lymphoplasmacytic lymphoma/Waldenström macroglobulinemia

BACKGROUND

Multi-parametric flow cytometry (MFC) is a helpful tool for detecting neoplastic cells in malignant lymphoma; however, lymphoma cells can be difficult to detect when characteristic immunophenotypic abnormalities are not evident. We evaluated the stainability of VS38, which is used for multiple myeloma, in normal and abnormal B cells using MFC to develop a new strategy for detecting lymphoma cells.

METHODS

We compared the median fluorescence intensity of VS38 staining in lymphocytes from patients without hematopoietic neoplasms and in B cells from 26 patients with B cell lymphoma (BCL). To evaluate the performance of VS38 gating, we compared VS38-positive B cells with the percentages of BCL cells, and with the mutation ratios of MYD88 L265P measured by droplet digital PCR in patients with lymphoplasmacytic lymphoma (LPL)/Waldenström macroglobulinemia (WM).

RESULTS

CD27-positive memory B cells were stained with VS38, whereas normal lymphocytes were faintly stained. Lymphoma cells were stained with VS38 in 11 of 12 patients with LPL/WM, 3 of 3 with chronic lymphocytic leukemia, 3 of 5 with mantle cell lymphoma, 2 of 4 with follicular lymphoma, and 1 of 1 with splenic marginal zone lymphoma. The percentages of VS38-positive B cells in VS38-positive BCL were equivalent to those of lymphoma cells and the mutation ratios of MYD88 L265P in LPL/WM.

CONCLUSIONS

VS38 identified neoplastic cells in plasma cell disorders and BCL. This might improve the accuracy of BCL diagnosis, especially in patients with LPL/WM.

Immunoglobulin M Paraproteinaemias

Monoclonal paraproteinaemia is an increasingly common reason for referral to haematology services. Paraproteinaemias may be associated with life-threatening haematologic malignancies but can also be an incidental finding requiring only observation. Immunoglobulin M (IgM) paraproteinaemias comprise 15–20% of monoclonal proteins but pose unique clinical challenges. IgM paraproteins are more commonly associated with lymphoplasmacytic lymphoma than multiple myeloma and can occur in a variety of other mature B-cell neoplasms. The large molecular weight of the IgM multimer leads to a spectrum of clinical manifestations more commonly seen with IgM paraproteins than others. The differential diagnosis of B-cell and plasma cell dyscrasias associated with IgM gammopathies can be challenging. Although the discovery of MYD88 L265P and other mutations has shed light on the molecular biology of IgM paraproteinaemias, clinical and histopathologic findings still play a vital role in the diagnostic process. IgM secreting clones are also associated with a number of “monoclonal gammopathy of clinical significance” entities. These disorders pose a novel challenge from both a diagnostic and therapeutic perspective. In this review we provide a clinical overview of IgM paraproteinaemias while discussing the key advances which may affect how we manage these patients in the future.