Extra-Acral Minute Synovial Sarcoma: A Case Report With Literature Review.

Synovial sarcoma is a malignant soft tissue tumor of uncertain differentiation. It is typically seen in the deep soft tissue of the extremities; however, it has been reported to occur anywhere in the body. Synovial sarcoma by histomorphology has multiple subtypes, including monophasic spindle cell, biphasic and poorly differentiated subtypes. Synovial sarcomas measuring less than one centimeter in diameter are termed "minute" synovial sarcomas. "Minute" synovial sarcomas have only been reported so far in the acral region of the hands and feet. They are extremely rare and can often be misinterpreted as benign neoplasms. Herein, we report the findings in a 30-year-old female presenting with a palpable mass within the deep subcutaneous tissue along the anterior aspect of her right rectus abdominis muscle. The mass was excised and measured 0.6 cm in greatest dimension with histomorphology findings, immunohistochemical and molecular workup confirming the diagnosis of "minute" synovial sarcoma. Our findings represent the first documented case of a "minute" synovial sarcoma occurring at an extra-acral site. With such unique finding not yet reported in the literature, this case highlights the importance of considering synovial sarcoma in the differential diagnosis of subcutaneous abdominal masses.