Primary Pulmonary Synovial Sarcoma With Extensive Myxoid Change Masquerading as a Lung Hydatid Cyst.

Synovial sarcoma is a rare malignant mesenchymal neoplasm primarily affecting adolescents and young adults, and it typically arises from deep soft tissues near large joints. Although commonly found in extremities, it can occur in various anatomic locations. We present a rare case of a 29-year-old man with primary pulmonary synovial sarcoma manifesting as a cystic mass masquerading as a lung hydatid cyst. Histopathologic examination, immunohistochemistry, and molecular analysis aided in accurate diagnosis. This case underscores the importance of considering synovial sarcoma in the differential diagnosis of pulmonary cysts and highlights the crucial role of pathologic examination in guiding treatment decisions.