CD5+ chronic B-cell leukemia with features intermediate to chronic lymphocytic leukemia and hairy cell leukemia

Chronic lymphocytic leukemia (CLL) and hairy cell leukemia (HCL) are differentiated B-cell leukemias with well-described clinical, morphologic, and immunologic characteristics. We encountered two patients with indolent chronic B-cell leukemia showing overlapping features of these malignancies. The patients had progressive splenomegaly, minimal lymphadenopathy, and abnormal lymphoid cells with abundant cytoplasm and villi, which were strongly positive for surface antigens CD22 and CD11c, features associated with HCL. However, blood counts showed lymphocytosis without neutropenia and monocytopenia, and the bone marrow biopsies demonstrated tightly aggregated nodules of lymphocytes. In addition, the lymphoid cells were dual positive for CD19 and CD5, displaying weak-to-moderately positive monoclonal surface immunoglobulin, findings strongly suggestive of CLL. One patient failed to respond to therapy with chlorambucil and prednisone. The second patient showed a partial response to treatment with 2-chlorodeoxyadenosine. We compare our patients with similar variants of differentiated B-cell leukemias reported in the literature, including disorders described as hairy cell variant (HCL-V) or splenic lymphoma with villous lymphocytes (SLVL).