ERBB2 and breast cancer: A significant positive association between ER expression and HER2-low expression was found in a cohort of 5235 patients with early HER2-low BC at the Dana-Farber Brigham Center; HER2-low expression did not seem to play a distinct prognostic role, and the authors found no statistically significant difference in the pCR rate and in OS between HER2-low and HER2-0 tumors, regardless of HR+ status [91,101,102].