Synovial Sarcoma-AV Malformation Collision in the Anterior Mediastinum.

Arteriovenous malformation (AVM) and synovial sarcomas are both rare lesions in the mediastinum. Rarer still is a collision tumor in that region. Herein we present a case of a collision tumor comprised of AVM and synovial sarcoma in a 76-year-old man, presenting with pneumonia. Imaging showed a vascular lesion that spontaneously ruptured, causing enlargement of the mass and hemothorax. The resected specimen revealed the malignant second component. This report is a discussion of the never-before reported lesion.