B cell lymphoma showing clinicopathological features of malignant histiocytosis.

This report describes a case of B cell lymphoma, the clinicopathological features of which are quite similar to those of malignant histiocytosis. The clinical features included fever, anemia, and marked hepatosplenomegaly without lymphadenopathy. Histological findings revealed diffuse and noncohesive proliferation of cytologically atypical cells and benign-appearing histiocytes in the splenic red pulp, where the erythrophagocytosis was frequently found. Immunological studies, however, revealed a B cell nature of proliferating atypical cells. Accordingly, the histology of this patient was interpreted as a neoplastic proliferation of B cells accompanied by marked proliferation and activation of the histiocytes.