An atypical breast lesion: bilateral multiple myoid hamartoma

A 41-year-old female presented at the department of radiology because of multiple slowly growing lumps in both breasts. Mammography showed dense breast tissue with multiple wellcircumscribed round lesions with no calcification. At ultrasound, sharply defined, heterogeneous oval masses were seen. On T2-Weighted Images (WI), the lesions were heterogeneous and hyperintense. T1-WI after intravenous administration of gadolinium contrast showed multiple rapidly and strongly enhancing lesions with type 2 to 3 curves (plateau and wash-out curve). Core needle biopsy reported bilateral multiple myoid hamartoma. Hamartoma of the breast is a benign proliferation of fibrous, glandular, and fatty tissue surrounded by a thin capsule of connective tissue. Breast hamartomas consist of approximately 0.7-5% of all benign breast tumors. The majority of these lesions occur in women over 35 years of age. The myoid or the muscular variant, Myoid Breast Hamartoma (MBH) is exceptionally rare with less than 30 reported cases in the English medical literature. The clinical, radiological and pathological features are discussed. The differential diagnosis includes other benign (e.g. multiple fibroadenomas, leiomyomas) and malignant breast lesions (e.g. leiomyosarcomas). A core biopsy is usually diagnostic for a myoid hamartoma, although excision and subsequent immunohistochemical examination is mandatory for definite diagnosis of this rare lesion.