Classification of lymphoma.

Classifications of B cell lymphomas are primarily designed for morphological diagnosis and are necessarily rigid in format, implying that clear distinctions exist between tumors composed of small lymphocytes, follicular center cells, immunoblasts, and plasma cells. This view may serve to obscure the interrelations of these neoplasms, for these cell types are not of separate lineage, but merely represent different morphological phases in the cell cycle of a single cell type--the B-lymphocyte. For lymphomas, as for neoplasia in general, the behavior of a tumor (benign vs malignant) may be predicted from the degree to which the neoplastic cells retain the function and form of the progenitor cell type. This review seeks to apply these principles to the diagnosis and classification of lymphocyte-derived neoplasms.