RESUMO
INTRODUCTION: This case report illustrates a rare case of teratoma of the mediastinum which was continuous to the pericardium and caused extrinsic compression to the right atrium. CASE PRESENTATION: A 22-year-old Caucasian man with no complaints or comorbid conditions presented to our hospital with obliteration of the right cardiophrenic sinus by a mass. A non-invasive investigation demonstrated a tumoral mass which was continuous to the pericardium and caused extrinsic compression to the right atrium. The clinical suspicion was a pericardial or bronchogenic cyst. Surgical and anatomopathologic findings led to the diagnosis of a mature cystic teratoma with atrophic thymic tissue at the external teratoma surface. CONCLUSION: We present an original report of a mature teratoma causing obliteration of the right cardiophrenic sinus with extrinsic heart compression. The diagnosis of this tumor is very difficult through non-invasive investigation.