Cowden's disease features facial trichilemmomas (a benign tumor of follicular epithelium), acral keratoses on the limbs, and oral mucosal papillomas and fibromas; it may also involve thyroid, gastrointestinal tract, ovaries, uterus, and breasts. Among 32 known cases of Cowden's disease, 21 are women, in 10 of whom breast cancer has already developed (bilateral in 4). The 11 women in whom breast cancer has not yet developed have fibroadenomas, fibrocystic disease, virginal hypertrophy of the breasts, and malformations of nipples and areolae. Their median age is only 36 years. Two have mothers with breast cancer and in one both mother and maternal grandmother had breast cancer. Dermatologic lesions, including pathognomonic multiple facial trichilemmomas, precede the development of malignancy and can identify women with a high risk of developing breast cancer.