Many lymphomas can be immunophenotyped by flow cytometry (FCM), providing valuable diagnostic information.1 However, FCM cannot typically be used to distinguish follicular lymphoma (FL), diffuse large B-cell lymphoma, germinal centre type (DLBCL-GCB) and diffuse large B-cell lymphoma, non-germinal centre type (DLBCL-nGCB).

To expand the utility of clinical FCM, we compared the expression of CD32, CD44, CD71 and forward and side light scatter in a series of DLBCL-GCB, DLBCL-nGCB and FL specimens, and compared the results to all B cells in non-neoplastic lymph nodes (follicular hyperplasia, FH). These studies demonstrate that germinal centre (GC) B-cell lymphomas (FL and DLBCL-GCB) show decreased expression of CD44, while CD71 tends to be increased in DLBCL relative to FL. Both DLBCL-nGCB and DLBCL-GCB showed increased side light scatter relative to low-grade FL and FH.

The project was completed under the approval of the Human Subjects Division of the University of Washington. 5 DLBCL-nGCB, 12 DLBCL-GCB, 15 FL grade 1–2 (FL1-2), 10 FL grade 3 (FL3; including 7 grade 3A and 3 grade 3B cases, grouped, given the small number of cases) and 6 FH were evaluated. MFI (median fluorescence intensity) and MLI (median light intensity, analogue of MFI) for forward light scatter (FSC) and side light scatter (SSC) were analysed in GraphPad Prism (V.10). Evaluation of differences between diagnoses was performed using Tukey’s multiple comparison test.

Cryopreserved specimens were thawed and diluted to yield at least 150 000 cells (where possible) and stained with a standard stain-lyse-wash procedure (combination in online supplemental table 1) using a protocol described previously.1 FCM studies were performed on a 17-colour LSR II flow cytometer and the data analysed using Woodlist V.3.1.3 (courtesy of Dr Brent L Wood). MFI (each antigen) and MLI were collected …