[De novo CD5-positive diffuse large B-cell lymphoma with leukemic dissemination diagnosed by immunohistochemical examinations of bone marrow clot sections].

A 61-year-old male visited his doctor in October 2000 because of a high fever. Laboratory examination revealed leukocytosis with blast-like cells and thrombocytopenia. He was referred and admitted to our hospital in November 2000. Although he had mild splenomegaly, he had no lymphadenopathy on the first admission. The white blood cell count was 10,520/microliter with 45% blast-like cells and the platelet count was 51 x 10(3)/microliters. Bone marrow aspiration revealed 82% blast-like cells, which were positive for CD5, CD10, CD13, CD19, and CD20. Immunohistochemistry of the bone marrow clot sections revealed blast-like cells were positive for CD5, but negative for TdT, CD23 and cyclin D1. We diagnosed the patient as having de novo CD5-positive diffuse large B-cell lymphoma (DLBCL) with leukemic dissemination. He obtained a complete remission after two courses of CHOP therapy. The third chemotherapy was postponed because of strangulation of the intestine. He relapsed and died in spite of the third chemotherapy. CD5-positive DLBCL is one of the established disease entities that requires an appropriate therapy regimen because it is characterized by elderly onset, extranodal involvement, and a poorer prognosis.