HER2 intratumoral heterogeneity is independently associated with incomplete response to anti-HER2 neoadjuvant chemotherapy in HER2-positive breast carcinoma

Purpose Anti-HER2 neoadjuvant chemotherapy has been widely used in HER2-positive breast cancer patients; however, pathologic complete response (pCR) is achieved in only 40–50% of patients. The aim of this study was to investigate the association of HER2 intratumoral heterogeneity (ITH) with response to anti-HER2 neoadjuvant chemotherapy.