Inversion of chromosome 16 and dysplastic eosinophils in accelerated phase of chronic myeloid leukemia

Abnormalities of chromosome 16, including inv(16)(p13q22), del(16)(q22), and t(16;16)(p13;q22), have been reported almost exclusively in association with acute myelomonocytic leukemia and are characteristically accompanied by abnormal eosinophlls with dysplastic granules in the bone marrow. We observed an inv(16)(p13q22) in two patients with typical Philadelphia chromosome positive chronic myeloid leukemia (CML). The appearance of the abnormality of chromosome 16 was associated with acceleration of disease or onset of blast crisis and with the appearance in the bone marrow of abnormal eosinophils. In both cases the marrow karyotypes were 46,XY,t(9;22)(q34;q11)/46,XY,inv(16) (p13q22),t(9;22)(q34;q11). In these two patients the temporal association of the acquisition of the inversion 16 and the appearance of monocytoid cells and dysplastic eosinophils in the bone marrow further supports the relationship of this karyotypic abnormality with leukemic monocytoid and eosinopnilic evolution. This secondary cytogenetic change appears to be an infrequent manifestation of specific phenotypic disease progression in CML.