Primary cutaneous diffuse large B‐cell lymphoma, NOS and leg type: Clinical, morphologic and prognostic differences

Summary Background and objectives Primary cutaneous diffuse large B‐cell lymphoma, NOS (PCLBCL/NOS) is a rare PCLBCL. Only few data are available for this tumor. The aim of this study was to identify clinical and/or immunohistochemical markers (in addition to Bcl‐2) that characterize PCLBCL/NOS, assist in differentiating it from PCLBCL, leg type (PCLBCL/LT) and help to assess the clinical course/prognosis. Patients and methods Bcl‐2– PCLBCL/NOS) cases (n = 14 were compared with Bcl‐2+ PCLBCL/LT cases (n = 29). Results PCLBCL/NOS patients were younger, predominantly male and had better survival rates than patients with PCLBCL/LT. Patients with PCLBCL/NOS presented more often with larger plaques limited to one or two contiguous body regions, whereas PCLBCL/LT cases often presented with disseminated lesions. Neoplastic cells had a higher proliferation rate (Ki67) in PCLBCL/LT patients. The tumor microenvironment of PCLBCL/NOS had a more prominent CD3+ infiltrate. Overall survival data for the whole cohort (n = 37) revealed that female gender and Bcl‐2 expression correlated with a worse survival rate. Bcl‐6 expression and centroblastic subtype correlated with better outcomes. None of the other markers studied (e.g. GCB/non‐GCB subtype) correlated with survival rate. Conclusions PCLBCL/NOS and PCLBCL/LT differ in their clinical behavior and outcomes. Bcl‐2 still seems to be the best marker for discriminating between these two subgroups. Bcl‐2, female gender and Bcl‐6 represent prognostic markers for PCLBCL.