ERBB2 and breast cancer: Triple-negative breast cancer cells (Hs578T, MDA-MB-231) show significantly less PpIX fluorescence compared with oestrogen-receptor-positive (T47D, MDA-MB-361) and HER2-positive cells (SkBr3, MDA-MB-453).23 Similarly, HER2 transformation of breast epithelial cells (MCF10A) doubled their PpIX fluorescence.