Chest Wall Synovial Sarcoma: A Unique Encounter at the Breast Base.

Synovial sarcomas most commonly arise in the para-articular locations of the extremities, such as the upper limbs, thigh, knee, ankle, and foot. Thoracic synovial sarcomas are a rare entity that can arise in the chest wall, pleura, lung, heart, or mediastinum. We present a case of a 23-year-old female with a complaint of swelling of the left breast. Examination demonstrated an enlarged left breast and a hard-fixed swelling without overlying skin changes or nipple retraction. Ultrasound showed a well-defined, solid-appearing lesion deep in the left breast parenchyma, which was adherent to the underlying left chest wall musculature and seemed to be displacing the breast parenchyma anteriorly. Contrast-enhanced computed tomography (CECT) and magnetic resonance imaging (MRI) confirmed the lesion centered at the left pectoralis major and minor muscles, confirming the chest wall's origin. Histopathology findings favored monophasic synovial sarcoma.