De novo CD5 Positive Diffuse Large B-cell Lymphomas with Bone Marrow Involvement in Korean

In CD5 positive (CD5+) mature B-cell lymphomas, newly recognized CD5+ diffuse large B-cell lymphoma (DLBCL) has been characterized by aggressive features. We studied twenty-five cases with CD5+ lymphomas involving bone marrow. Eleven cases were diagnosed as chronic lymphocytic leukemia, six cases were diagnosed as mantle cell lymphoma (MCL), and three cases with morphologic characteristics of MCL and without both the cyclin D1 expression and IGH/CCND1 rearrangement were unclassifiable. The remaining five cases, showing large to medium-sized lymphoid cells with prominent nucleoli and a moderate amount of cytoplasm, were diagnosed as DLBCL. Five DLBCL cases were positive for CD5, CD20, surface immunoglobulin, but negative for CD23. Patients with CD5+ DLBCL showed a high age of onset (median, 68 yr) and two patients expired one month after the diagnosis. Since CD5+ DLBCL forms a distinct subgroup of DLBCL, a study of CD5 expression in DLBCL would be helpful to predict prognosis and to determine future therapeutic strategy. To the best of our knowledge, this is the first report on de novo CD5+ DLBCL in Koreans.