Giant mammary hamartoma diagnosed by stereomicroscopic analysis of the mammary glandular tree in an adolescent girl: report of a case.

This report describes a rare case of a giant hamartoma that developed in the right breast of a 17-year-old girl. No abnormalities were found by endocrinological studies and a well-circumscribed tumor, approximately 20 cm in diameter, was easily enucleated without bleeding during surgery, following which the bilateral breasts became nearly symmetrical. Histologic features revealed predominant fibrous stroma and scattered normal or occasionally dysplastic mammary glands without neoplastic properties. No distorted lobular structures indicating fibroadenoma characteristics were observed. Subgross and stereomicroscopic analysis of serial 2-mm-thick sections revealed mature normal lobules and predominant fibrous interstitial components. Therefore, the tumor was diagnosed as a giant hamartoma of the breast, according to the histologically non-neoplastic features and the delimited macroscopic appearance. This is a rare mammary gland disease characterized by the fact that although each of the histological components seemed to be normal, their constitution was abnormal. It appears that not only histological features but also clinical details are indispensable for the diagnosis of this disease.