ERBB3 and neoplasm: Numerous studies in recent years have highlighted an expanding role of HER3 in tumor progression [75,76,77,78,79,80,81,82,83,84,85,86,87], showing that its heightened cell surface density is associated with drug resistance (especially resistance to targeted inhibitors) and metastasis, including metastasis to the brain [75,76,81,88,89,90,91,92].