Rupture of bronchogenic cyst in the pericardium with high carbohydrate antigen 19-9 production

Mediastinal bronchogenic cysts are frequently detected incidentally in adults. Here, we present a unique case of atypical clinical course of bronchogenic cyst beneath the carina, which ruptured into the pericardium. We could not diagnose definitely at initial admission, even though the massive pericardial fluid was exudative with high carbohydrate antigen (CA) 19-9 production. The fluid cytology was negative for malignancy. Five years later, the regrown and unruptured bronchogenic cyst caused atrial fibrillation by impinging on the heart with a high level of serum CA19-9. After resection of the CA19-9-enriched cyst by thoracoscopic surgery, he was discharged without recurrence of atrial fibrillation or any chest symptoms, and the serum CA19-9 level decreased to within the normal range. Differential diagnosis of cytology negative pericardial effusion with high CA19-9 production may be difficult, however, intrapericardial rupture of bronchogenic cyst should be considered in some patients.