ERBB2 and invasive ductal breast carcinoma: Using FISH, eight tumors displayed amplification of the HER2 gene (DIN1C-3: n = 2; invasive ductal carcinoma: n = 6), one tumor had an equivocal score (HER2/chromosome 17 ratios: 1.6-2,1) and one tumor showed polysomy 17 (HER2/chromosome 17 ratio: 1.1).