Think Outside the Heart: An Unusual Cause of Large Hemopericardium

Pericardial effusions secondary to tumors are commonly metastatic, originating primarily from the lung, breast, and lymphomas. Pericardial tamponade is a rare oncological emergency warranting early identification and treatment. We describe a 66-year-old male found to have a large bloody pericardial effusion causing tamponade physiology, and multimodality imaging was consistent with intrapericardial malignancy with no identifiable primary source. He was subsequently diagnosed with type B3 thymoma after mediastinal resection.