The leukemia from which the human cell line HL-60 was derived was classified in 1976 as acute progranulocytic leukemia (APL), although it was recognized to show a number of atypical features. In the ensuing 10 years, the concept of APL and its integral association with t(15;17) has evolved, and the concept of APL as a morphologically recognizable entity has become embodied in the term French-American-British classification M3 (FAB-M3). It is now recognized that not every case of leukemia with a high proportion of progranulocytes can be classified as FAB-M3. We reviewed the light and ultrastructural morphology of the original diagnostic material from this case, and we report that the leukemia from which HL-60 was derived does not conform to the currently recognized entity of FAB-M3 and is more appropriately classified as an acute myeloblastic leukemia with maturation, FAB-M2.

Cytogenetic studies were performed in 546 patients with acute leukemia between 1968 and 1975. Two hundred thirty-four patients were aneuploid (42.9%), and 312 patients were diploid (57.1%). Among these, 32 patients were found to exhibit similar chromosomal alterations that appeared to involve specifically chromosomes 8 and 21. Banding studies in at least 15 of these patients confirmed the presence of a translocation between these two chromosomes. The cytogenetic findings were correlated with the hematologic and clinical data. It was found that each of these individuals had a typical picture of acute granulocytic leukemia with Auer rod-positive and peroxidase-positive cells. Ultrastructurally, the patients in this group also consistently demonstrated the presence of a nuclear bleb that has been positively associated with aneuploidy in acute leukemia. Clinically, they seemed to respond better to therapy than other adult patients with acute granulocytic leukemia. It is proposed that the 8/21 translocation acute leukemia represents a definite subgroup within the general category of acute granulocytic leukemia, with an incidence of approximately 7.3%.