In vitro colony-forming characteristics of chronic granulocytic leukemia in childhood.

Peripheral blood from a child with adult-type (Philadelphia chromosome positive) chronic granulocytic leukemia was found to contain large numbers of cells capable of colony formation in tissue culture. The majority of the colonies contained granulocytic cells. The source of these granulocytic colonies was found in a population of myeloblasts, promyelocytes, and myelocytes which could be separated from the more mature granulocytic cells of the peripheral blood by sedimentation of the buffy coat on Ficoll-Hypaque. The predominance of granulocytic colonies is in contrast to our observations previously made on the peripheral blood of children with "juvenile" type(Ph1 chromosome negative)CGL in which large numbers of exclusively monocytic colonies were produced in tissue culture. These current studies, when interpreted in light of relevant clinical data, suggest that the "juvenile" and "adult" types of CGL represent two very different forms of chronic leukemia in childhood. The Ph1 chromosome negative form may be classified as a monocytic leukemia with a granulocytic component but the Ph1 chromosome positive adult form, even when it occurs in a child, appears to be a true granulocytic leukemia.