Localized Blastoma Preceding Blastic Transformation in Ph1‐Positive Chronic Myelogenous Leukaemia: Morphological and Cultural Studies of the Transformation Event

In a patient with Ph1-positive chronic myelogenous leukaemia (CML), the development of a localized blastoma preceding generalized blastic transformation was accompanied by a reduction of granulocyte-macrophage (GM) colony forming capacity in agar of bone marrow cells as well as an increase in peripheral neutrophil alkaline phosphatase (NAP) scores. Successful transplantation of the blastoma cells into nude mice enabled extensive studies of the cell properties. The blastoma cells were double Ph1-positive cells which did not respond to human granulocyte-macrophage colony-stimulating factor (GM-CSF), and were similar to cells demonstrated in spleen and bone marrow at the terminal stage of the patient's illness. These observations clearly support the case for sequential studies of colony formation in vitro as a useful test for the early detection of disturbances in marrow function that may occur before generalized blastic transformation. Studies of the properties of the blastoma cells also provide some insight into possible mechanisms for the transformation event.