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Context.—: Unlike B-cell acute lymphoblastic leukemia/lymphoma (ALL/LBL), there have been few therapeutic advances in T-cell ALL (T-ALL)/LBL, an aggressive ALL/LBL subtype., Objective.—: To perform a focused tissue array study to elucidate tumor markers of therapeutic potential in T-ALL/LBL., Design.—: Using immunohistochemistry, we evaluated expression of leukemic antigens of interest, specifically CC-chemokine receptor 4 (CCR4), among others, on available remnant diagnostic material, including tumor tissue slides obtained from formalin-fixed, paraffin-embedded preserved tissues., Results.—: Our analysis identified, for the first time, expression of CCR4 in T-ALL/LBL in 11 of 27 cases (40.7%) and confirmed common expression of BCL2, CD38, and CD47, as reported previously. We also identified the expression of CD123 in 4 of 26 cases (15.4%), whereas BCL6 and PDL1 were expressed in a small number of T-ALL/LBL cases. The potential novel target CCR4 was significantly more common in the Pre/Pro-T immunophenotypic subtype, 6 of 9 (66.7%, P = .01). No additional differences in clinical and epidemiologic variables were noted among positive or negative CCR4 cases., Conclusions.—: These findings support preclinical and clinical testing of therapies targeting CCR4, CD47, BCL2, CD38, and CD123 in T-ALL/LBL, and may help guide the development of targeted clinical trials in T-ALL/LBL, a rare disease in urgent need of novel therapies., (© 2024 College of American Pathologists.)

Flow cytometry (FC) has a well-established role in the diagnostic evaluation of mature B-cell neoplasms. Effective assessment for lineage associated antigens, aberrant antigen expression, and immunoglobulin light chain restriction requires a well-designed, optimized, and controlled FC assay. However, it is important for hematopathologists to know when flow cytometry has a more limited role, and other modalities, such as immunohistochemistry, cytogenetic and molecular testing, are more important. This review will discuss the features of an optimal FC assay for the evaluation of mature B-cell neoplasms, and the current role of FC in the diagnosis and sub-classification, prognostic assessment, identification of therapeutic targets, and assessment for disease response to therapy. © 2018 International Clinical Cytometry Society., (© 2018 International Clinical Cytometry Society.)

Background: Although many clinical laboratories are adopting higher color flow cytometric assays, the approach to optimizing panel design and data analysis is often traditional and subjective. In order to address the question "What is the best flow cytometric strategy to reliably distinguish germinal center B-cell lymphoma (GC-L) from germinal center hyperplasia (GC-H)?" we applied a computational tool that identifies target populations correlated with a desired outcome, in this case diagnosis., Design: Cases of GC-H and GC-L evaluated by flow cytometric immunophenotyping using CD45, CD20, kappa, lambda, CD19, CD5, CD10, CD38, were analyzed with flowType and RchyOptimyx to construct cellular hierarchies that best distinguished the two diagnostic groups., Results: The population CD5-CD19+CD10+CD38- had the highest predictive power. Manual reanalysis confirmed significantly higher CD10+/CD38-B-cells in GC-L (median 12.44%, range 0.74-63.29, n = 52) than GC-H (median 0.24%, 0.03-4.49, n = 48, P = 0.0001), but was not entirely specific. Difficulties encountered using this computational approach included the presence of CD10+ granulocytes, continuously variable B-cell expression of CD38, more variable intensity antigen staining in GC-L and inability to assess the contribution of light chain restriction., Conclusion: Computational analysis with construction of cellular hierarchies related to diagnosis helped guide manual analysis of high dimensional flow cytometric data. This approach highlighted the diagnostic utility of CD38 expression in the evaluation of B-cells with a CD10+ GC phenotype. In contrast to computational analysis of non-neoplastic cell populations, evaluation of neoplastic cells must be able to take into consideration increased variability in antigen expression., (© 2013 Clinical Cytometry Society.)

Flow cytometric immunophenotyping (FCI) is recommended in the evaluation of cerebrospinal fluid (CSF) specimens for hematologic neoplasms. This study reviewed FCI of CSF specimens collected for primary diagnosis (n = 77) and follow-up for known malignancy (n = 153). FCI was positive in 11 (4.8%) of 230 specimens: acute myeloid leukemia, 6; precursor B-acute lymphoblastic leukemia, 2; B-cell lymphoma, 2; and T-cell lymphoma, 1. Positive results were obtained in low-cellularity specimens, including 2 with fewer than 100 events in the population of interest. FCI was indeterminate in 19 (8.3%) of 230 specimens, including 3 with only sparse events, 8 with possible artifact (apparent lack of staining, nonspecific or background staining, and aspirated air), and 8 with phenotypic findings considered insufficient for diagnosis. Indeterminate specimens were often limited by low cellularity and lacked normal cell populations to evaluate for appropriate staining. FCI may be of value in low-cellularity CSF specimens, although the results should be interpreted with caution.

Evaluation of B-lymphocytes is one of the most well-established clinical applications of flow cytometric immunophenotyping. This article addresses general principles of the flow cytometric evaluation of B-cell lymphoid neoplasms, followed by discussion of how flow cytometric data can assist in determining a list of diagnostic possibilities and directing additional testing.

Two translocations involving the MALT1 gene have been described in extranodal marginal zone B-cell lymphomas of MALT type. A t(11;18)(q21;q21) involving API2 and MALT1 occurs in a subset of MALT lymphomas but with only rare exception is absent in diffuse large B-cell lymphomas (DLBCL), even at MALT sites. More recently, a t(14;18)(q32;q21) involving IGH and MALT1 has been described in nongastric extranodal MALT lymphomas. This translocation is indistinguishable from the IGH-BCL2 translocation by using classical cytogenetics. We report the IGH-MALT1 translocation in a cutaneous DLBCL as shown by classical cytogenetics and molecular cytogenetic analysis. This is the first report of an IGH-MALT1 translocation in DLBCL. These findings indicate that MALT1 translocations are not restricted to indolent-appearing lymphomas, provide further evidence that API2-MALT1 and IGH-MALT1 translocations exhibit biologic differences, have implications regarding the pathogenesis of some extranodal DLBCL, and emphasize that a t(14;18)(q32;q21) cannot be assumed to reflect a BCL2 translocation.

Recent reports have indicated that the neoplastic T cells of angioimmunoblastic T-cell lymphoma express CD10. It has been suggested that the demonstration of a CD10+ T-cell population may assist in establishing a diagnosis of angioimmunoblastic T-cell lymphoma and in distinguishing angioimmunoblastic T-cell lymphoma from other peripheral T-cell lymphomas. It has been unclear, however, whether this phenotypically unusual T-cell population might be present in other settings as well. In this report, we have retrospectively examined 64 cases of lymph node and solid tissue biopsies for the presence of CD10+ T cells using multicolor flow cytometry. Discrete populations of CD10+ T cells were found in 5 of 28 cases (18%) of reactive lymphoid hyperplasia, 4 of 17 cases (23%) of follicular lymphoma, and 9 of 19 cases (47%) of marginal zone B-cell lymphomas. The CD10+ T cells constituted 1-6% of total cells analyzed and

Flow cytometric analysis is important in the diagnosis, classification, and follow-up of non-Hodgkin lymphoma. It is assumed that the lymphoma phenotype for each patient remains unchanged over time and is consistent from one specimen to another. To determine the variability in expression of lymphoid antigens, we reviewed 211 flow cytometry specimens of malignant lymphoma from 81 patients. Some antigens showed a stable pattern of expression such as CD5, CD10, CD19, CD20, and HLA-DR. In contrast, CD21, CD22, CD23, and CD25 showed more variability from one specimen to another. We believe several factors affect the stability of antigen expression. True differences in expression most probably are related to the biology and function of the different antigens. For instance, CD19 and CD20 are essential in cell maturation and function and, therefore, are present on the majority of cells. In contrast, CD22 has a role during B-cell activation and, therefore, is more variable. Lack of standardization inflow cytometry procedures also is responsible for some variability. Instrument settings for adequate compensation and the criteria used to determine when an antigen is reported as positive are important considerations when evaluating flow cytometry histograms.