In comparison of FISH and karyotyping techniques on the PB and BM specimens, the obtained results were similar, but in one CML patient under imatinib therapy, FISH was able to detect BCR-ABL fusion in 30% of interphase blood cells, whereas in the G-banding, no Ph chromosome on the metaphases was observed. Here, BCR is linked to chronic myelogenous leukemia, BCR-ABL1 positive.