Recent progress in our understanding of the immune system and the development of new techniques that permit the precise identification of lymphocytes have permitted a reexamination of lymphoid neoplasms. Most of the non-Hodgkin\u27s lymphomas and lymphocytic leukemias have been characterized as T or B cell neoplasms and have been shown to possess features similar to those expressed by normal lymphoid cells at different stages of maturation. The clinical significance and therapeutic implications of these discoveries are now being explored. This paper presents a concise overview of the differentiation of human B lymphocytes, the surface and cytoplasmic markers that permit their recognition, and the diverse tumors that are now known to be malignant counterparts of normal B cell elements. Particular emphasis is placed on the utility of surface and cytoplasmic immunoglobulin as unique B cell markers and on the clonal nature of B cell tumors
