CD5-Positve Diffuse Large B-Cell Lymphoma Presenting in Bone Marrow without Lymphadenopathy

Abstract

In this study, we reported five cases of CD5⁺ diffuse large B-cell lymphoma (DLBCL) which initially presented as bone marrow involvement without lymphadenopathy. The cases involved two males and three females, with an average age of 73.8 years. The patients had fever and showed general fatigue. Three of the five cases presented hepatosplenomegaly. Laboratory examination highlighted anemia, thrombocytopenia, presence or absence of leukopenia, hypoalbuminemia as well as a considerable elevation of serum lactate dehydrogenase, soluble IL-2R and ferritin. Bone marrow aspiration smears showed large-sized lymphoma cells, which were found to aggregate, and clot sections showed many clusters of lymphoma cells, which had a large and round or indented nucleus with vesicular chromatin and occasional small nucleoli. Mitotic rate was high. In the bone marrow clot section, whereas three cases exhibited a diffuse infiltration of the lymphoma cells (diffuse type), two cases exhibited a sinusoidal proliferation (intravascular type). Cytogenetic analysis showed many and complex abnormalities in all 3 cases examined. The lymphoma cells were positive for CD5, CD19, CD20, CD38, IgM, bcl-2 and bcl-6, while they were negative for CD3, CD10, CD23, CD30, cyclin D1 and TdT. In four cases, after a semi-nested PCR amplification of the immunoglobulin heavy chain (IgH) gene, a discrete band could be detected. All the cases exhibited an in-frame sequence and the frequency of somatic mutations ranged from 2.1 to 11.1% with no intraclonal diversity. These DLBCL may have derived from the same counterpart as CD5⁺ B-CLL. There were no differences in laboratory, immunological and molecular examination between the diffuse type and the intravascular type. Recurrences in the bone marrow and an aggressive clinical course were also observed in both types.