p53 mutations and/or p53 protein accumulation have been reported in 13% to 70% of invasive intraductal carcinomas of the breast [5, 15–23] and have also been detected in ductal carcinoma in situ [5, 20–22], in benign breast disease [24–28], in normal-appearing breast tissue [28], and in women at high risk of breast cancer [29]. This evidence concerns the gene TP53 and breast fibrocystic disease.