Case Report: Giant esophageal duplication cyst mimicking cardiac compression in an adult.

Background Esophageal duplication cysts (EDCs) are rare congenital foregut malformations, accounting for only 0.5 to 2.5% of all esophageal masses. Although typically diagnosed during childhood, adult presentations are uncommon and frequently characterized by asymptomatic progression or non-specific clinical features. We report the case of a 58-year-old male presenting with atypical chest pain and anxiety. Multimodal imaging (CT and MRI) revealed a massive posterior mediastinal mass measuring 12 × 11 cm that exerted significant mechanical compression on the left atrium. The patient underwent a successful right posterolateral thoracotomy for surgical resection. Histopathological examination confirmed the diagnosis of an esophageal duplication cyst. The postoperative course was uneventful, with complete resolution of symptoms. Giant EDCs should be considered in the differential diagnosis of mediastinal masses in adults, even when presenting with atypical cardiovascular symptoms. Surgical resection remains the definitive treatment of choice to prevent long-term complications and establish a formal histological diagnosis.