Studies suggest that ER-positive, HER2-positive breast tumors may rely on both the endocrine and HER2 pathways for growth, and that patients with such tumors may derive less benefit from chemotherapy than those with ER-, HER2-positive breast cancer [14, 15, 17, 18] Pathologic investigations support these clinical observations. The gene discussed is ERBB2; the disease is breast neoplasm.