ERBB3 and neoplasm: The protein has a central role in driving oncogenic signals in tumours,4 and preclinical and clinical data have led to the hypothesis that HER3 is an escape pathway to EGFR blockade through a compensatory shift to HER3 signalling, predominantly through the PI3K/AKT pathway.5, 6, 7 Moreover, clinical data indicate that HER3 overexpression predicts the lack of efficacy of panitumumab.8