A case of monoblastic crisis of CML beginning with extramedullary tumor formation in a rib

A patient with CML showed monoblastic crisis which started with extramedullary tumor formation in a rib before medullary involvement. She was diagnosed as having CML in 1984 at the age of 57. In February 1990, she was admitted to Furukawa City Hospital because of extramedullary blastic crisis beginning at the right 5th rib. At that time, the bone marrow revealed 4.6% blasts. On March 5, after one course of chemotherapy, she was transferred to our hospital for radiotherapy. Hematological findings were WBC 10,100/microliter with 10% blasts, Hb 10.9 g/dl, platelet 3.7 x 10(4)/microliters. Bone marrow aspiration was unsuccessful. The blasts in the peripheral blood were negative for peroxidase and chloroacetate esterase; but positive for naphtylbutyrate esterase. The leukemic cells were positive for CD13, CD33, and had phagocytic activity. Chromosomal analysis revealed 46XX with Ph1 chromosome and some additional anomalies. Southern blot analysis of tumor cells shows BCR rearrangement. These findings suggest that the blasts were immature monocytic cells, and we conclude that this is a rare case of extramedullary monoblastic crisis of CML.