ERBB2 and breast carcinoma: However, the pCR does not appear to have a prognostic impact on luminal breast cancer patients, especially among low-grade and HER2-negative tumors.6, 37 Although we could not identify independent predictors of pCR, all tumors with pCR were ductal, had high histological grade, Ki67 expression > 14%, and most were HER2-positive.