Characteristics of Lymphoproliferative Disorders with More Than One Aberrant Cell Population as Detected by 10-Color Flow Cytometry

Biclonal Low-Grade B Cell Lymphoma as Detected by Multiparametric Flow Cytometry in Blood and Marrow

Biclonal B cell lymphomas (BCL) of two different low-grade components are rare. Multiparametric flow cytometry (MFC) is an integral tool in lymphoma diagnosis and very efficient in picking up BCL cases, especially when the associated second component is small. We studied the incidence of BCL in the routine blood and marrow samples sent for immunophenotyping by MFC. A total of 376 cases were analyzed retrospectively. We studied their clinical, immunophenotypic, molecular, and cytogenetic findings with literature review. We found five cases of BCL with two different clonal low-grade B cell components at an incidence of 1.3%. All cases were males with a median age of 68 years. The chronic lymphocytic leukemia (CLL) clone was present in all 5 cases. The other associated component in cases 1 to 5 were lymphoplasmacytic lymphoma, follicular lymphoma, splenic marginal zone lymphoma, hairy cell leukemia, and monoclonal B cell population of non-CLL type respectively. Diagnosing BCL may be challenging and may also go undiagnosed when the second component is petite and overshadowed by the more significant component. It may be critical if the small, unnoticed lymphoma component is of a more aggressive type.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12288-022-01625-y.

Flow Cytometry of CD5-Positive Hairy Cell Leukemia

BACKGROUND AND OBJECTIVE

Hairy cell leukemia (HCL) is a chronic lymphoproliferative disorder for which diagnosis is typically straightforward, based on bone marrow morphology and flow cytometry (FC) or immunohistochemistry. Nevertheless, variants present atypical expressions of cell surface markers, as is the case of CD5, for which the differential diagnosis can be more difficult. The aim of the current paper was to describe diagnosis of HCL with atypical CD5 expression, with an emphasis on FC.

METHODS

The detailed diagnostic methodology for HCL with atypical CD5 expression is presented, including differential diagnosis from other lymphoproliferative diseases with similar pathologic features, by FC analysis of the bone marrow aspirate.

RESULTS

Diagnosis of HCL by means of FC started by gating all events based on side scatter (SSC) versus CD45 and B lymphocytes were selected from the lymphocytes gate as CD45/CD19 positive. The gated cells were positive for CD25, CD11c, CD20, and CD103, while CD10 proved to be dim to negative. Moreover, cells positive for CD3, CD4, and CD8, the three pan-T markers, as well as CD19, showed a bright expression of CD5. The atypical CD5 expression is usually correlated with a negative prognosis and thus chemotherapy with cladribine should be initiated.

CONCLUSION

HCL is an indolent chronic lymphoproliferative disorder and diagnosis is usually straightforward. However, atypical expression of CD5 renders its differential diagnosis more difficult, but FC is a useful tool that allows an optimal classification of the disease and allows initiation of timely satisfactory therapy.

Flow cytometry-Recognizing unusual populations in leukemia and lymphoma diagnosis

Flow cytometry is an invaluable technology in the examination of blood, bone marrow, tissue and body fluids for the presence or absence of hematological disease. It is used in both diagnostic and follow-up testing, with an increasingly important role in the detection of very small residual disease populations (Minimal Residual Disease, MRD) However, flow cytometry immunophenotyping of leukemia and lymphoma is highly dependent on interpretation of results and with the increased complexity of 8-10 color instruments routinely used in clinical laboratories, knowledge of disease-defining populations is increasingly important as is recognizing normal and reactive patterns. This manuscript presents case studies with flow cytometric patterns encountered in routine screening of samples sent for leukemia and lymphoma immunophenotyping, focusing mainly on B-cell disorders which may be missed or incorrectly interpreted by the laboratory (including a hematopathologist) performing the test. Case studies are used to illustrate our laboratory's standardized approach to the interpretation of flow cytometric data. In addition to a standardized approach, these cases emphasize the importance of interpretative skills of technologist and hematopathologists in recognizing abnormal patterns in detecting hematological malignancies.