Incidental Irregular Mass Within a Hamartoma Detected on Breast Ultrasound: A Case Report and Review of the Literature

Mammary hamartomas are heterogeneous breast masses containing glandular epithelium, fibrous tissue, and adipose tissue. The development of a breast carcinoma within a hamartoma is rare. We present the case of a 41-year-old female patient who had an asymptomatic breast mass incidentally discovered on physical exam. Ultrasound indicated a benign-appearing mass encased in a hamartoma. Fifteen months later, follow-up imaging detected a new hypoechoic irregular mass with an angular margin. Further work-up with biopsy identified the mass to be a fibroadenoma. In hypoechoic masses with suspicious features such as irregular shape and angular margins, malignancy cannot be definitively ruled out without a core needle biopsy. Radiological identification of these masses, which appear distinct from heterogeneous hamartomas, allows for early detection of potential carcinomas. To distinguish carcinomas from fibroadenomas, these masses should be biopsied.