Isolated subacute effusive and nonconstrictive epicarditis masquerading as a right atrial mass

Epicarditis (visceral pericardial inflammation) is a very unique and rare diagnosis. It is almost always associated with parietal pericardial involvement and may occur in medical conditions such as viral, bacterial (mycobacterial) infections and uremia or postoperatively in the setting of cardiac surgery. Frequently, no etiology is found. Most cases are associated with constrictive physiology, and patients present with symptoms and signs of right-sided heart failure. Effusive epicarditis is often present, and the clinical features may easily be confused with those of pericardial effusion with tamponade. We report a unique case of isolated subacute effusive and nonconstrictive epicarditis mimicking a right atrial mass in a 72-year-old patient who was diagnosed with nonmetastatic gastric adenocarcinoma. Our case is unique for several reasons: inflammation was limited to the epicardium (very few cases have been described to date); the patient was asymptomatic, with no clinical or echocardiographic evidence of constriction (this represents a novel finding, explained in part by the more limited extent of inflammation, with no significant fibrotic component and no parietal pericardial involvement); and this is the first report of epicarditis occurring in association with a malignancy, which we hypothesize may represent an inflammatory paraneoplastic process.