The level of HER2 expression in the selected cell lines is considered to be 20,000–50,000 receptors/cell (19) which correlates with clinical data regarding HER2 expression in PCa and corresponds to the very low expression in BCa (+1 according to a HercepTest), where tumor biopsies with a score of 1+ (a faint/barely perceptible membrane staining in >10% of tumor cells) are considered to present negative HER2-expression, however, a score of 3+ (strong complete membrane staining is observed in >10% of tumor cells) is considered to present strong positive HER2-expression (8). The gene discussed is ERBB2; the disease is neoplasm.