What is the most likely diagnosis?

D. The case presents a patient with bicytopenia, increased population of mature-appearing lymphocytes in peripheral blood with ample basophilic cytoplasm and condensed chromatin. Close examination of the surface of lymphocytes reveals the presence of small, irregularly distributed villous projections. Bone marrow biopsy exhibits nodular lymphoid aggregates, and flow cytometry reveals lack of expression of CDS, CD10, and CD23. This clinical presentation is most consistent with splenic marginal zone lymphoma, a subtype of marginal zone lymphoma. SMZL is uncommon, comprising about 2% to S% of lymphomas. Patients present with splenomegaly, sometimes massive, with minimal or no peripheral lymphadenopathy. Hepatitis C has been described in association with SMZL. Lack of CD10 expression differentiates SMZL from FL, which is usually CD10 positive. Lack of expression of CDS differentiates SMZL from MCL, and lack of CDS and CD23 expression is useful in ruling out SLL/CLL. Nodular involvement of the bone marrow is useful in distinguishing SMZL from HCL, which usually presents with diffuse bone marrow involvement rather than a nodular pattern seen in SMZL (Blood. 2003;101(7):2464, Br 1 Haematol. 2003;122(3):404, Blood. 2002;100(S):1 648, Leukemia. 2008;22(3):487, Cancer. 2004;101(9):20SO).