ATF3 and carcinoma: The carcinomas that develop in multiparous BK5.ATF3 mammary glands express a wide range of marker proteins, characteristic not only of both basal and suprabasal compartments of the mammary gland (CK5 and CK8, respectively), but also the suprabasal compartments of the interfollicular epidermis (K10) and the hair follicles (mIRSa.2, mIRSa.3.1).