Most Diffuse Large B-Cell Lymphomas Are Identified by Flow Cytometry
Alexandra M Harrington, Horatiu Olteanu, Steven H Kroft. Medical College of Wisconsin, Milwaukee, WI
Background: Diffuse large B-cell lymphoma (DLBCL) is one of the most common lymphomas identified in tissue biopsies during routine practice. Various references have propagated the perception that DLBCLs are difficult to assess by flow cytometry (FC) given their large cell size, fragility, and frequent association with necrosis/debris, sclerosis, and increased mitotic activity. Notably, however, there is essentially no data to substantiate this. Failure to identify an abnormal large B-cell population by FC may increase turnaround time and possibly misdirect subsequent immunohistochemical evaluation. Anecdotally, we have observed high rates of DLBCL detection by FC in tissue specimens and therefore chose to systematically study this observation.
Design: We retrospectively analyzed in a blinded fashion 4-color FC data from tissue specimens containing DLBCL. The following antibodies were assessed routinely: CD5, CD10, CD19, CD20, CD23, CD38, FMC7, monoclonal and polyclonal anti-kappa and anti-lambda. Reactive, polyclonal lymphoid tissue specimens served as (-) controls. Bone marrow and fluid specimens were excluded. Lymphoma populations were identified using cluster analysis and defined as FC(+) based on immunophenotypic aberrancy and/or light chain restriction. FC cytospin morphology was reviewed in select cases.
Results: We collected 68 DLBCLs (35 females and 33 males), 21-92 y/o (median 63) and 11 (-) controls (7 females and 4 males), 19-88 y/o (median 54). The DLBCL specimens included 22 soft tissues (ST), 19 lymph nodes (LN), 6 bone, 4 each of mediastinum, lung, and sinonasal, 3 retroperitoneal, 3 brain, and 1 each of skin, bowel, and spleen; the (-) controls consisted of 8 LNs and 3 tonsils. FC was (+) in 53/68 (78%) DLBCLs, ranging from 0.03-75% of events (median 9%). FC was (-) in all controls. Abnormal B-cells were not identified in 15/68 (22%) DLBCLs, which included 2/4 (50%) lung, 5/22 (23%) ST, 6/19 (32%) LN, and the spleen and bowel specimens (1 each). Of 12 FC(-) cases with available cytospins, 9 (75%) contained morphologically evident lymphoma cells and 3 had no intact cells.
Conclusions: Abnormal B-cell populations were identified in 78% of DLBCL tissue specimens by FC, highlighting its use as an important diagnostic study in aggressive B-cell lymphomas. To the best of our knowledge, this is the first study to detail the detection rate of DLBCLs in tissues. Interestingly, the majority of FC(-) cases had morphologic evidence of lymphoma in the processed FC specimens; the cause of the (-) analyses in these cases is unclear.
Tuesday, March 20, 2012 1:00 PM
Poster Session IV # 210, Tuesday Afternoon