Proliferative lesion of anogenital mammary-like glands in the setting of Cowden syndrome: case report and review of the literature.

Mammary-like glands are normal appendages of anogenital skin and can give rise to epithelial and stromal tumors that closely resemble breast tumors. Cowden syndrome is an autosomal-dominant cancer-predisposition syndrome that is associated with increased risk of various benign and malignant tumors including breast cancers. Here, we report the first case of a proliferative lesion of mammary-like glands in the setting of Cowden syndrome. A 27-year-old female with Cowden syndrome (R130Q-PTEN mutation) presented with a 1-cm tender, polypoid perianal lesion. An excisional biopsy revealed a circumscribed, lobulated lesion with fibromyxoid stroma and epithelial hyperplasia with apocrine and columnar cell changes that was arranged in papillary, micropapillary and focal cribriform architecture. The features strikingly resembled proliferative changes commonly seen in the breast. Interestingly, the patient subsequently developed an atypical complex sclerosing lesion of the breast. Given the increased risk of breast neoplasia in Cowden syndrome, and the morphologic relationship between breast glands and mammary-like glands, this case raises the possibility of an increased risk of neoplasia arising in mammary-like glands in the setting of Cowden syndrome.