A Rare Presentation of a Fibrous Breast Hamartoma Requiring Careful Imaging Assessment.

Breast hamartomas are benign disorders and are generally composed of breast-constituting pathological components, mainly fat components. A 68-year-old woman was found to have a left breast mass on computed tomography (CT) for coronary artery evaluation due to suspected angina pectoris. Mammography showed a well-defined oval mass, 2.7 cm in size, without obvious fat findings in the upper and outer quadrant of her left breast. Ultrasound showed a well-circumscribed mass with predominant low internal echoes, high internal echoes in very small areas, weakly enhanced posterior echoes, and no blood flow into and around the mass. Magnetic resonance imaging (MRI) of the breast mass showed low signals on T1-weighted images, predominant low signals on fat-suppressed T2-weighted images, and no enhancement through early-to-late-phase images on dynamic studies. The patient, therefore, underwent a core needle biopsy, which unfortunately only showed abundant fibrous components and no malignant cells, leading to no definitive pathological diagnosis. We, therefore, treated the breast mass with a lumpectomy to get both a pathological diagnosis and a cure of the presumed benign breast mass. The bisected mass had whitish cut surfaces except for the core needle biopsy-induced hemorrhage areas. Postoperative pathological study showed predominant fibrous components, a small amount of adipocytes, and sparse mammary duct-lobular structures in the fibrous components, leading to the diagnosis of fibrous breast hamartoma. The patient recovered uneventfully and is scheduled to receive annual mammography follow-ups. Diagnostic physicians should note that breast hamartomas can have predominant fibrous components.