An unusual B-cell lymphoma simulating hairy cell leukemia.

The authors report an unusual B-cell lymphoma that simulated hairy cell leukemia (HCL) not only clinically but also pathologically in peripheral blood, bone marrow, and lymph node specimens. A diagnosis of lymphoma could be made only after pathologic examination of the spleen, indicating that caution should be exercised in making a primary diagnosis of HCL on bone marrow examination. Morphologically this lymphoma resembled monocytoid B-cell lymphoma (MBCL) but the immunophenotype (monoclonal Ig-kappa +, Ia+, B4+, Leu-1+, LN-2+, lambda-, Bl-, LN-1- and CALLA-) and clinical findings were more consistent with mantle zone lymphoma (MZL). Because this case demonstrates features of both MBCL and MZL, the authors suggest that these two entities may have a common histogenesis.