A hamartoma is a benign tumor composed of various tissues, and one of its locations may be the breast. Patients can present with a painless, asymptomatic and well-demarcated palpable mass in a breast hamartoma. Imaging studies such as mammography, ultrasonography, and magnetic resonance imaging (MRI) show specific radiologic features, whereas a biopsy, either fine needle aspiration or core needle, may be sometimes necessary to confirm the diagnosis.
Defined as a well-established mass with a still incomplete etiology, hamartoma is a rare benign tumor that contains a mixture of different tissues (fibrous, adipose, glandular, and potentially other) in various proportions   . Numerous sites in the body may be the location of its development, including the breast, and between 4-8% of all benign breast lesions, are attributed to hamartomas . This benign tumor has been reported across different age groups after puberty  , but the majority of patients are women in their 30s and 40s    . The clinical presentation is characterized by the presence of a sharply defined, painless, and asymptomatic oval or round-shaped mass in the breast area that is freely palpable    . The nodular appearance of the mass is accompanied by its smooth surface and a soft consistency . However, studies show that up to 60% of breast hamartomas are not possible to palpate, and are thus interpreted as subclinical tumors . Hamartomas are most commonly found in the outer quadrants, and it is not uncommon for the diagnosis to be made incidentally during evaluation of other breast-related pathologies  . Additional symptoms are not present in the setting of hamartomas, which is one of the main clinical features of this tumor . Furthermore, breast hamartomas are mobile and not attached to the surrounding muscle or skin tissue, which might be an important clinical sign as well  .
A detailed physical examination, together with a properly obtained patient history, is the first and perhaps most important step in order to make the diagnosis of a breast hamartoma. Adequate palpation of both breasts and the respective quadrants can result in detection of a mass, after which the use of various imaging studies might be employed. Various procedures have been mentioned, one of the more useful being mammography, the gold-standard procedure in the assessment of breast tissue  . A nonhomogeneous mass composed of adipose, fibrous and glandular tissue that is often enclosed by a thin capsule is the hallmark of a breast hamartoma on mammography, but the variability in the percentage of fat and glandular/connective tissue might pose a challenge to the physician   . For this reason, ultrasonography (US), but also MRI, might be used as adjunctive or even superior methods compared to mammography  . Main findings on the US are the absence of a retrotumor acoustic phenomenon, which is frequently found in malignant lesions  . On MRI, breast hamartomas are visualized as heterogeneous lesions with a sharp and clearly delineated capsule described as a hypointense rim . As mentioned previously, the distribution and dominance of different tissues may necessitate for a biopsy sample to be obtained, either by a core needle biopsy or a fine needle aspiration (FNAC), both valuable in the workup of this tumor   .