The application of fluorescence in situ hybridization in detecting chronic myeloid leukemia

Abstract

To evaluate the clinical significance of the application of fluorescence in situ hybridization (FISH) in detecting chronic myeloid leukemia (CML). Chromosome preparation was made by using 24-hour culture. FISH technique using dual color dual fusion (DC-DF) BCR/ABL probe was performed in all 158 cases and R-banding was also employed for karyotyping in some patients. Among the 158 cases, 98 cases were Ph positive, of which 69 cases (70.4%) were typical FISH pattern (1R1G2F), the other 29 cases (29.6%) showed 12 different types of atypical FISH pattern. The most frequent atypical patterns found were 1R1G1F in 7 cases (7.1%), 2R1G1F in 5 cases (5.1%), 1R1G2F and 1R1G3F in 4 cases (4.1%), 2R2G1F in 3 cases (3.1%). Karyotype analysis on 18 CML cases with atypical FISH patterns demonstrated that the atypical FISH patterns were due to variant translocation in 3 cases; the additional third signal was because of a supernumerary Ph chromosome. The karyotyping results did not conform to FISH results in four cases suggesting the conceivable mistakes in karyotyping. The 1R1G1F signal pattern seen in 3 cases with classical t(9;22) resulted from the deletion of derivative chromosome 9. The 1R1G2F signal pattern detected in 40% to 64% of interphase cells of 3 cases without Ph chromosome by conventional cytogenetic analysis suggested a submicroscopic translocation. Three cases treated with Glivec or bone marrow transplantation showed normal karyotypes with a small amount of BCR/ABL positive cells by FISH detection. FISH technique is of great value for the diagnosis of CML and confirmation of variant translocation, occult Ph translocation, derivative chromosome 9 deletion, therapeutic effect of interferon and Glivec as well as detection of minimal residual disease after bone marrow transplantation.