A CD5+ leukemic lymphoma with monocytoid features: an unusual B-cell lymphoma mimicking hairy-cell leukemia.

A case of lymphoma presenting with features shared by hairy cell leukemia (HCL) and its variant, intermediate lymphocytic lymphoma (ILL) and monocytoid B-cell lymphoma (MBCL) is described. Clinical presentation and the morphological findings observed in peripheral blood and in bone marrow biopsy suggested an HCL; however, the tartrate-resistant acid phosphatase negativity of peripheral blood lymphocytes, the histologic pattern observed in the spleen, and the immunophenotyping of peripheral blood, spleen and bone marrow neoplastic lymphocytes (expression of CD5 and lack of CD25), were strongly against this hypothesis. The clinical course was aggressive. This report emphasizes the concept of the equivocal presentation of some 'low-grade' B-cell lymphomas. It is further pointed out that, even with complete and exhaustive morphological and immunological analyses, atypical cases may be encountered.