Double Ph-positive megakaryoblastic transformation of chronic myeloid leukemia

A 64-yr-old Japanese man presented with mild anemia, leukocytosis, and thrombocytosis in November 1999. A diagnosis of chronic myeloid leukemia was made with a positive Ph chromosome, and interferon α treatment was started, 6 million units a day. Two years later, in October 2001, the patient developed leukocytosis, an increased LDH level, and large blasts with basophilic cytoplasm with cytoplasmic projections appeared in the peripheral blood. Bone marrow aspiration revealed increased blasts (59.6%). These blasts were negative on peroxidase stain, positive on acid phosphatase, and weakly positive on α naphthyl butyrate esterase stain and periodic acid-Schiff stain. Immunohistochemical staining with monoclonal antibodies revealed that these blasts were strongly positive with anti-CD41 (glycoprotein IIb/IIIa), weakly positive with CD7, CD33, and CD34, and negative with other monoclonal antibodies. A diagnosis of megakaryoblastic transformation from chronic myeloid leukemia was therefore made. Two-color fluorescence in situ hybridization (FISH) for portions of the major-bcr and abl genes from bone marrow cells revealed two fused signals in 90.6% and one fused signal in 5.8% of 106 cells. A cytogenetic study revealed that bone marrow cells were 69, XYY, + 6, -7, + 8, -9, t(9;22)(q34;q11), + 11, + 13, - 15, - 16, dic(17;18)(p11;p11), - 18, + 19, + 21, der(22)t(9;22) in six of nine examined cells. These findings confirmed that these megakaryoblasts originated from megakaryocytes of the chronic myeloid leukemia clone.