Expression of EGFR in mammary glands and spontaneous breast cancer tissues from TA2 mice. 2A, EGFR staining could be observed occasionally in epithelial cells in mammary gland tissues from five-month-old TA2 mice (IHC, 200×). 2B and 2C, EGFR staining was localized to both the cytoplasm and nucleus in mammary gland tissues from spontaneous breast cancer-bearing TA2 mice (IHC, 200×). 2D, Nuclear EGFR was also present in spontaneous breast cancer tissues from TA2 mice (IHC, 200×). Mammary gland tissues and tumor tissues from cancer-bearing TA2 mice expressed higher levels of EGFR than those of mammary gland tissues of five-month-old TA2 mice.