[Monocytoid B-cell lymphoma: clinico-pathologic study of 2 cases]

Monocytoid B-cell lymphoma, considered as a low-grade lymphoma, is seen most frequently in persons of advanced age, chiefly women. It is often diagnosed in lymph-node phase, in low stages (I-II), and peripheral blood, bone-marrow or spleen are seldom involved. The morphologic and immunohistochemical study of two patients with monocytoid B-cell lymphoma is presented. The characteristic cell morphology, with homogeneous nuclei, low number of mitoses, and clear, wide cytoplasm, was present in both. Tumour cells expressed CD45, CD20, HLA-DR and monoclonal IgM-lambda and lambda chains, respectively. Case no. 1 had more irregular nuclei, protruding nucleoli, advanced stage at diagnosis and shorter clinical course. An epithelioid granulomatous reaction was present in case no. 2, which delayed the diagnosis until relapse. The diverse forms of clinical onset of monocytoid B-cell lymphoma, as well as its possibly aggressive course, association with other types of lymphoma and the difficulties for an adequate morphologic identification are commented.