Philadelphia chromosome-negative, bcr/abl-positive chronic myelogenous leukemia.

Chronic myelogenous leukemia(CML)is characterized by the presence of the abnormal chromosome 22, which is termed the Philadelphia chromosome(Ph). The Ph is derived from a translocation between chromosomes 9 and 22, t (9; 22)(q 34; q 11). The c-abl oncogene on the long arm of chromosome 9 fused to the bcr gene on the long arm of chromosome 22 and leads to the formation of a chimeric bcr abl gene located on the Ph. The chimeric bcr abl gene produces 8.5-kb bcr abl transcript and chimeric fusion protein, p 210 BCR ABL. The p 210 BCR ABL protein plays a central role in the leukemogenesis of CML. The case shown in the Figures was a rare Ph-negative CML case having typical clinical findings of CML. In these Ph-negative CML cases, in addition to cytogenetic analysis, molecular biological analyses such as fluorescence in situ hybridization(FISH)and spectral karyotyping(SKY)FISH are used as potential tools for diagnosis. FISH and SKY FISH are used as an adjunct to standard G-banding karyotyping(Fig. 1)to achieve a higher sensitivity and specificity. FISH and SKY FISH provided additional cytogenetic information including the clarification of complex chromosomal rearrangements . The present SKY FISH revealed a translocation between chromosomes 2 and 9(Fig. 2), and FISH revealed a chimeric bcr abl gene on chromosome 22(Fig. 3). From these findings, the present case was finally diagnosed as a Ph-negative and bcr abl-positive CML.