Robotic excision of an ectopic thymoma in the cardiophrenic angle presenting as a cystic mediastinal mass

Thymomas most commonly arise in the anterior mediastinum, whereas ectopic thymomas occurring outside the normal thymic bed are rare. Lesions arising in the cardiophrenic angle can pose a diagnostic challenge, as they may mimic other mediastinal cystic lesions on imaging. We report the case of a 43-year-old male who was incidentally found to have a well-defined lesion in the right cardiophrenic angle on contrast-enhanced computed tomography. The mass appeared as a heterogeneously enhancing solid-cystic lesion closely abutting the pericardium, raising suspicion for a cystic mediastinal lesion. The patient underwent robotic-assisted thoracoscopic excision of the mass. Intraoperatively, the lesion was well encapsulated and separable from surrounding structures. Complete excision was achieved without the need for pericardial resection. Histopathological examination confirmed the diagnosis of a thymoma. This case highlights the diagnostic challenges associated with unusual mediastinal masses and demonstrates the feasibility and effectiveness of robotic-assisted minimally invasive resection.