ERBB2 and neoplasm: However, due to the implicit rarity of such antigens, many commonly targeted solid tumor antigens, such as human epidermal growth factor receptor 2 (ErbB2), epidermal growth factor receptor (EGFR), mucin 1 (MUC1), prostate-specific membrane antigen (PSMA), and disialoganglioside (GD2)10, are also expressed by non-tumor tissues, albeit at lower levels.