Taking into account the heterogeneity of the most common breast cancer types and also to test the possible cytotoxic effects of MB-PDT in normal-like cells, we used the following human breast epithelial cell lines: MCF-7, an ER, PR and HER-2-positive, luminal A cell line; MDA-MB-231, a TNBC cell line; and MCF-10A, a normal-like cell line. The gene discussed is ERBB2; the disease is breast carcinoma.