The existence of lymphoid lineage restricted Philadelphia chromosome-positive acute lymphoblastic leukemia with heterogeneous bcr-abl rearrangement

Analysis of lineage involvement was performed in 17 Philadelphia chromosome -positive acute lymphoblastic leukemia patients with no history of chronic myeloproliferative disorder. The percentage of blastic cells as defined by flow cytometry matched that of the Ph-positive cells in 14 out of 17 patien ts. The bcr-abl rearrangement was investigated by fluorescent in site hybri dization in morphologically identified blastic cells, myeloid elements, lym phocytes and erythroblasts using a combined light and fluorescent microscop ical imaging. Lymphoid lineage restriction could be determined in all but t hree of the patients. These 14 patients exhibited heterogeneity in terms of m-bcr and M-bcr types of translocation as revealed by reverse transcriptio n polymerase chain reaction. The three patients with multilineage involveme nt and M-bcr type of translocation reverted to chronic phase and the percen tage of Ph-positive cells remained high. Thus, we could identify an uncommi tted stem cell origin among Ph-positive ALLs only in those patients whose d isease subsequently proved to be a lymphoid blastic crisis with clinically silent chronic phase.