Large mammary hamartoma with focal invasive ductal carcinoma.

Mammary hamartomas are uncommon benign lesions rarely associated with malignancy. We report a case of a 25-year-old female patient presenting with a lump in the left breast. Fine needle aspiration cytology showed features of invasive ductal carcinoma along with normal benign glands that were mistaken for normal breast tissue. However, the mastectomy specimen revealed the malignant mass within a larger hamartomatous mass. Mammary hamartomas are benign lesions but, on exceedingly rare occasions, they may be involved by incidental, coexisting carcinoma, as illustrated in this case report.