ERBB2 and breast cancer: Indeed, we observed co-segmental amplification of HER2 and the pericentromeric 17p and/or 17q region in 74% of HER2‒amplified cases according to MIP microarray; none of these cases were true polysomy 17, which supports previous studies’ conclusions that true polysomy 17 in breast cancer is rare [37, 39, 40].