Null cell (non-T, non-B) acute lymphoblastic leukemia terminating as malignant histiocytosis

A case of null cell acute lymphoblastic leukemia (ALL) terminating in malignant histiocytosis (HMR) is discussed. The patient was a 22-year-old man who presented in January 1976 with ALL. Cell surface markers on the bone-marrow blasts showed that 1% formed rosettes with sheep erythrocytes (T cells) and 4% showed immunofluorescent staining for immunoglobulin; terminal transferase levels were elevated, confirming the diagnosis of null cell ALL. The patient was treated intensively with a combination of chemotherapy and cranial irradiation. One year after diagnosis, he was maintained in partial relapse (10-15% blasts). His terminal episode was characterized by pancytopenia. The bone marrow was replaced by malignant histiocytes. Cell surface membrane staining for cytophilic antibody was positive, whereas terminal transferase levels were in the range of nonlymphoid malignancies.