Chronic myelogenous leukemia (CML) is the only h a m a n neoplastic disease associated with a specific cytogenetic abnormality, the Philadelphia (Phl) chromosome. This marker chromosome is found in the majority of patients with CML and has only occasionally been reported in other hematologic conditions. I t has been reported previously in 12 patients with acute myelogenous leukemia (AML), and it has been suggested that these cases may represent the blastic crisis of CML presenting without the usual chronic and relatively "benign" phase. W e have recently had the opportunity to observe two such patients. I t would appear that this is not a rare phenomenon and that it has received inadequate emphasis in the literature. Some patients with CML may present without a previous history of disease and with a morphological picture similar to AML, with only the finding of the Phl chromosome to separate these cases from true AML. Since the response to treatment of AML and the blastic crisis of CML appears to be different, the differentiation of these two entities may be of importance in the evaluation of therapeutic responses.
HRONIC MYELOGENOUS LEUKEMIA (CML) IS
C the only human neoplastic disease associated with a specific cytbgenetic abnormality, the Philadelphia (Phl) chromosome. It is generally conceded to represent a number 21 autosome with a foreshortened long arm. A growing body of evidence points to the acquired nature of this G-group abnormality. This marker chromosome is found in bone marrow cells in the majority of patients with CML and has only rarely been reported in other hematologic conditions, especially other myeloproliferative syndromes. It has occasionally been reported in patients with acute myelogenous leukemia (AML), and it has been suggested that these may represent the blastic crisis of CML presenting without the usual chronic and relatively "benign" phase of the disease.2" We have recently observed two such patients. CASE REPORTS Case 1. E.M. (UMH #1079315), a 29-year old Caucasian man, was referred to the Uni-From the