RESUMO
BACKGROUND: Clonal proliferation of monocytoid B-lymphocytes (MBLy)--monocytoid B-cell lymphoma (MBCL) represents a "new" type of lymphoma within the spectrum of B-cell malignancies. OBJECTIVES: The aim of the study was to evaluate the possibilities of a routine histological and immunohistochemical diagnosis of MBCL. METHODS: Three cases of MBCL diagnosed in peripheral lymph nodes (n = 2) and in mammary gland with infiltration of regional lymph node (n = 1) were analyzed both histologically and immunohistochemically using a panel approach (Ig chains, CD30 antigen, markers of B-cells, T-cells and of monocytes/histiocytes). RESULTS: Morphological appearance of neoplastic cells of MBCL is identical to that of MBLy in reactive conditions--kidney-shaped nuclei, bright clear PAS-negative cytoplasm, and small inconspicuous nucleoli. CONCLUSIONS: Morphological appearance together with immunophenotypic results (positivity of CD20 and Ki-B5, negativity of CD3, CD43, CD45RO, and of lysozyme, negativity of CD30) are considered to represent sufficient diagnostic criteria of MBCL, including its differential diagnosis of other B-cell low grade malignancies. An increase of large cell type MBLy might represent a feature of a secondary blastic transformation of MBCL. (Tab. 2, Fig. 5, Ref. 27.)