[Anterior mediastinal cyst disclosed by protracted thoracic pain]

The authors report a case of anterior mediastinal cyst discovered incidentally in a 71-year-old man presenting with prolonged chest pain and a history of chronic renal failure secondary to polycystic kidney disease. The diagnosis of these cysts, which are benign congenital tumours usually asymptomatic and with a favourable course, was established by thoracic CT. In difficult cases, magnetic resonance imaging allows precise analysis of pericardial masses. Clinicians should think of this possibility in the presence of an opacity of the cardiophrenic angle associated with chest pain.