Immunophenotypic profile of lymphoplasmacytic lymphoma/Waldenström macroglobulinemia.

We retrospectively reviewed the immunophenotypic profile of 75 cases of lymphoplasmacytic lymphoma/Waldenström macroglobulinemia (LPL/WM) analyzed by flow cytometry. All patients had monoclonal IgM (median, 2,100 mg/dL [21 g/L]) in serum and were considered clinically to have WM. The neoplastic cells, in all cases, expressed monoclonal immunoglobulin light chain (k, 55; l, 20) and CD19, and every case assessed was positive for CD20 (n=68) and CD52 (n=60). The results for other antigens assessed in decreasing frequency of positivity were as follows: surface IgM (26/28 [93%]), CD79b (11/13 [85%]), CD11c (13/16 [81%]), CD25 (5/7 [71%]), CD23 (17/28 [61%]), CD38 (24/50 [48%]), FMC7 (11/29 [38%]), CD22 (4/12 [33%]), CD5 (3/65 [5%]), and CD10 (1/38 [3%]). These results show that the immunophenotype of LPL/WM is variable and overlaps with other B-cell lymphoproliferative disorders. CD23, usually of dim intensity, and CD11c are expressed commonly in LPL/WM. Rare CD5+ and CD10+ cases of LPL/WM also exist.