Myoid Hamartoma of the Breast: A Case Report

Abstract

Breast hamartomas are rare benign breast neoplasms containing various tissues (1-4). A myoid (muscular) hamartoma is a very rare subtype of hamartomas occurring in the presence of smooth muscle cells (1,2). Although a few reports described myoid hamartoma, they rarely introduced detailed sonographic findings of that lesion. We encountered a young patient with myoid hamartoma and presented the mammographic, sonographic, and histopathologic findings. Case ReportA 28-year-old woman presented with a non-tender, movable mass in her left breast over the last several months. Her medical and family history was unremarkable. Upon physical examination, the mass was found to measure about 3 cm and located in the left upper outer quadrant. No abnormality was found in the overlying skin and no axillary lymphadenopathy. Her general condition was good.A mammography was performed for the evaluation of the mass, and showed no definition due to the patient's dense breast, but was suspected to show some bulging on the contour of the upper left portion of the breast (Fig. 1). On ultrasonography, this mass showed about a 4.2×2.5 cm sized isoechoic solid mass with a focal inhomogeneously low echoic portion. The mass revealed a parallel orientation and posterior acoustic enhancement, lobulated shape, focal angular and microlobulated margin, and increased vascularity in the peripheral region (Fig. 2). No abnormal lymphadenopathy was found on ultrasonography. We suspected this mass to be a fibroademona or phylloides tumor, and categorized it as 4a according to BIRADS (Breast Imaging Reporting and Data System) lexicon.Fine needle aspiration biopsy and microscopic results suggested a ductal hyperplasia. The patient underwent a local excision under general anesthesia. The macroscopic appearance showed a partially encapsulated, rubbery pale yellow, solid mass without necrosis or hemorrhage. The histological findings indicated the presence of smooth muscle cells intermingled with lobular tissue, and a scanty amount of fibrous tissue; however, no remarkable adipose tissue was found. The immunochemistry results were positive for actin and SMMHC Myoid (muscular) hamartoma is a rare subtype of hamartoma and is characterized by the presence of smooth muscle cells. We report a case of myoid hamartoma presenting as a large palpable mass in a 28-year-old patient, which was confirmed by surgical excision and pathologic diagnosis.