ERBB2 and breast cancer: However, 45% to 55% of these patients with BC defined as HER2 negative actually have HER2 low expression (IHC 1+ or 2+, but FISH negative) (4), and recent reports show that no survival benefit could be obtained from the combination of HER2-targeted therapeutics with chemotherapy among women with HER2 low-positive BC (5–7).