For many years, mammary hamartoma was considered to be an under-diagnosed disease. However, with the increasing use of diagnostic procedures in breast tumors (mammography, ultrasound, fine needle aspiration cytology and core needle biopsy), diagnosis of this entity has increased. Mammary hamartomas normally manifest as painless, mobile, palpable lumps without adherence to skin or muscle. Mammography shows well-circumscribed tumors, separated from adjacent normal breast tissue. Macroscopically they are well-defined tumors, consisting of benign mammary glandular tissue, fibrous stroma and fat in variable proportions, sometimes with a pseudoencapulation. Because of the lack of cytological and architectural specificity of hamartomas, correlation between clinical manifestations, imaging techniques and histology is essential. This report describes a case of an 11-cm mammary hamartoma in a 46-year-old woman.