Cell population analysis of a heterogeneous blast cell crisis of chronic myelogenous leukemia.

A case of Philadelphia negative chronic myelogenous leukemia (CML) is described with the following features: 1) initial lymphoid blast crisis; followed by 2) a heterogeneous blast crisis including myeloid, monocytic, and lymphoid elements that could be distinguished by morphological, cytochemical, ultrastructural methods and by immunologic markers; and 3) clonal evolution as shown by methylcellulose cultures and ultrastructural studies with emergence of a relatively drug resistant subclone of leukemic cells. Determination of surface antigen phenotype in CML blast crisis thus provides clinically useful information for the structuring of treatment protocols. This study also confirms previous studies that lymphoid blast crisis of CML can occur in Ph'-cases and that the Philadelphia chromosome is probably a clonal marker only and its presence is not directly related to the subsequent clinical course of the disease.