A large mediastinal mass in a 33 year old patient.

Mediastinal masses are commonly found during the evaluation of other illnesses. During gynecologic evaluation for suspected endometriosis, a large asymptomatic intrathoracic mass was discovered in the patient presented. After pre-operative evaluation, the patient underwent thoracotomy with removal of a mature, cystic teratoma invading the pericardium. Invasion of the pericardium is rarely seen with these lesions. The diagnosis of teratoma is difficult to make based solely on radiologic or clinical findings and must be confirmed at pathology for final diagnosis.