Ductal carcinoma in situ arising in mammary hamartoma

Hamartoma of the breast is an uncommon lesion. Although it can possess characteristic radiological features, the pathological appearance is not distinctive. Hamartoma is generally considered benign, but four cases have been reported with ductal and lobular carcinoma arising in hamartomas. This report describes further cases of hamartoma from which ductal carcinoma in situ arose, with one showing early invasion. In both cases, the tumours were within the hamartomas and were adequately excised during lumpectomies of the hamartomas, and the patients were well afterwards. This report emphasises the importance of adequate sampling of mammary hamartoma.