[Philadelphia chromosome-negative chronic myelogenous leukemia with trisomy 13].

Trisomy 13, as a sole karyotypic abnormality in acute leukemia, has been reported in several cases. However, in chronic myelogenous leukemia (CML), only two cases with this abnormality were reported so far. We describe herein a 68-year-old case with Philadelphia chromosome-negative CML and trisomy 13. Leukocytosis was pointed out during the treatment for other diseases. After 7 months, abrupt increase in leukocyte count (108,000/microliters) and splenomegaly developed. Decreased neutrophil alkaline phosphatase activity and morphological features fulfilled the diagnostic terms for CML. However, the karyotypic analysis revealed trisomy 13 instead of Philadelphia chromosome, and the BCR gene rearrangement was not detected. In cases with acute leukemia accompanied by trisomy 13, malignant transformation of an immature hematopoietic precursor cell has been suggested by the expression of antigens characteristic of both the myeloid and lymphoid lineage. In a few cases with myelodysplastic syndrome, a multipotent stem cell disorder, trisomy 13 has also been reported. From these standpoints, there might be a possibility that trisomy 13 as a sole abnormality in hematologic disorders would be related to tumorigenesis in the levels of multipotent stem cells.