Abstract
Mammary hamartomas are uncommon breast lesions, sometimes presenting as mammographic abnormalities which require pathological clarification. Previous cases have all been benign. A unique case of mammary hamartoma containing atypical lobular hyperplasia (ALH), lobular carcinoma in situ (LCIS), and foci of microinvasive lobular carcinoma is presented. The need for adequately sampling macroscopically innocuous breast lesions is emphasised.