Parafollicular (or monocytoid) B-cell lymphoma (PBCL) is a recently described low grade lymphoma. The relationship of parafollicular B cells to other B lymphocytes is not known, but the authors observed plasmacytic differentiation in the initial case of PBCL. In this report 12 cases of PBCL were studied by light microscopy and immunophenotypic analysis, and plasmacytic differentiation was found in four cases. This plasmacytic differentiation and the anatomic relationship of the neoplastic cells to reactive follicular centers suggest a functional relationship between these cell types.
