ERBB3 and breast cancer: One explanation to elucidate the HER3 survival context in HER2-amplified breast cancer subtype could be related to intensified HER2 signalling because of paradoxical HER2 homodimerization in carcinomas with concurrently low HER3 but high HER2 expression due to amplified HER2. It has been previously confirmed that HER2 homodimerization is frequent, especially in breast carcinomas characterized by HER2 gene amplification, and is related to reduced RFS [17].