We present here a rare case of Philadelphia chromosome (Ph)-positive chronic myelogenous leukemia having p190 BCR/ABL with a malignant clinical picture of extramedullary blast crisis at onset, followed by rapid evolution to bone-marrow blast crisis. The patient was a 44-year-old woman presenting with leukocytosis and multiple lymph-node swelling in the neck. Lymph-node biopsy revealed a myeloperoxidase-positive blastoma with cell-surface markers of myeloid and T-lymphoid lineages. Fluorescence in situ hybridization and the reverse transcription polymerase chain reaction detected a minor BCR breakpoint but failed to detect a major BCR breakpoint. By single-strand conformation polymorphism and direct sequencing, no alteration in the TP53 gene was found, and no additional chromosomal abnormalities other than Ph were identified. The present case suggests that p190 BCR/ABL is associated with the aggressive course of the disease.