a nodular, benign breast lesion occurring most frequently in relatively young women and consisting of hyperplastic distorted lobules of acinar tissue with increased collagenous stroma; the changes may be difficult to distinguish microscopically from carcinoma. Additionally, a benign nodular microscopic lesion of the prostate consisting of acinar tissue with increased stroma; the basal cell layer shows characteristic smooth muscle metaplasia. SYN: adenofibrosis, fibrosing adenomatosis, fibrosing adenosis.