Amplification of c-myc by fluorescence in situ hybridization in a population-based breast cancer tissue array

A total of 261 primary breast carcinomas were analyzed for amplification of the c-myc oncogene by fluorescence in situ hybridization performed on tumo r tissue array samples. Results were compared with individual clinicopathol ogic and follow-up data. Thirty-eight (14.6%) of the tumors showed c-myc ge ne amplification (defined as two or more additional copies of c-myc gene in relation to the number of chromosome 8 centromere). The reproducibility of fluorescence in situ hybridization assay (defined by hybridization with tw o different myc probes) was good (kappa coefficient 0.402). Statistically s ignificant associations were found between c-myc amplification and DNA aneu ploidy (P=.0011), and progesterone receptor negativity (P=.0071), and c-myc amplification also tended to be associated with high histologic grade (P=. 064), positive axillary nodal status (P=.080), and a high S-phase fraction (P=.052). c-myc amplification was not significantly associated with overall survival of patients with invasive cancer (P=.32). These data from a popul ation-based tumor material suggest that c-myc amplification is a feature of aggressive breast cancers, but that it is unlikely to be a clincially usef ul prognostic factor.