ERBB2 and breast cancer: Although the associations between TOP2A amplified and several clinicopathological factors, including larger T, high nuclear grade, and high Ki67 index, were significant, almost TOP2A amplified was observed in HER2 positive breast cancers; specifically, the rates of TOP2A amplified were 42.2% (57/135) and 0.8% (4/508) in HER2-positive and -negative cancers, respectively.