Aneuploidies of chromosome 17 in breast cancer: Relative prevalence in a series of 170 patients from Córdoba, Argentina, studied with fluorescent in-situ hybridization (FISH)
e22195 Background: The amplification of HER-2 oncogen, located in 17q11.2–12, occurs in 20–30% of invasive breast cancer. Numerical anomalies of chromosome 17 are frequent findings in these patients, during the study of the amplification of HER-2 oncogen with FISH technique, though clinical implications are yet not defined. Objectives: To determine the presence of chromosome 17 aneuploidies in a series of patients with histological diagnosis of breast cancer and to correlate these data with amplification and overexpression of HER-2 oncogen. Methods: Samples of 170 patients included in paraffin were analyzed with FISH technique, using the PathVysion system. We analyzed the number of HER-2 oncogen specific signals and chromosome 17 centromere (CEP 17) signals. We followed the ASCO 2007 guidelines to evaluate FISH and immunohistochemical analysis (IHC). Criteria for aneuploidy: diploid at 1.5–2.25 average CEP 17 signals /cell; hyperdiploidy: values over 2.25 and hypodiploidy: lower than 1.5. Results: We found 73 cases of chromosome 17 aneuploidies (42.9%), 68/73 polysomies (93%) and 5/73 monosomies (7%). The monosomies were observed in 4/5 patients with HER-2 amplification. Polysomies occurred simultaneously with HER-2 amplification in 48% (35/73), 45% (33/73) were not amplified and 7% (5/73) were equivocal. FISH and IHC could be correlated in 136 patients: the higher percentage of polysomies observed corresponded to groups IHC+3/HER-2+ (46%) and IHC+2/HER- (29%). Polysomy 17 was detected in 3 cases IHC+3/HER-2-. Conclusions: The relative prevalence of chromosome 17 aneuploidy in our series was 43%. According to the literature, this finding in 3 patients IHC+3/HER-2- could be responsible for the overexpression of protein cerbB2. The clinical effect of chromosome 17 aneuploidy continues under study. No significant financial relationships to disclose.