Primary cutaneous diffuse large B cell lymphoma (DLBCL), leg type, subcutaneous mass

DLBCL, leg type, occurring predominantly as a subcutaneous mass at a non-leg site in an 89-year-old woman with history of diffuse large B cell lymphoma (DLBCL) involving the dermis/subcutaneous tissue of the left shoulder two years earlier, presented with a slow growing 6 cm subcutaneous mass.
(A) Localized on positron emission tomography/computed tomography scan to the right lower abdominal wall.
(B) A diffuse monotonous proliferation of large lymphocytes with a centroblast-like or rarely immunoblastic appearance.
(C) The tumor cells strongly express BCL2.
(D) The tumor cells strongly express IRF4/ MUM1.
The tumor cells only focally express BCL6 and lack CD10 (not shown). This immunophenotype was the same as the earlier DLBCL; fluorescence in situ hybridization demonstrated a complex karyotype (not shown) with multiple MYC signals (also present in the earlier DLBCL). The patient was treated with rituximab, cyclophosphamide, hydroxydaunorubicin, Oncovin (vincristine), and prednisone or prednisolone (R-CHOP) and was in complete remission at 15 months' follow-up.