Abstract
A 64-year-old woman complaining of progressive dyspnea was admitted with recurrence of massive pericardial effusion. The patient had been diagnosed with radiation pericarditis based on a previous case of pericardiocentesis. To make a diagnosis and improve her symptoms, imaging examinations and pericardial fenestration were performed. Because of difficulty making a diagnosis, after some months, pericardiotomy and incision of the epicardium were performed. The patient was ultimately diagnosed with primary malignant pericardial mesothelioma of the epithelioid type. Primary malignant pericardial mesothelioma is a rare tumor that is difficult to diagnose. An antemortem diagnosis can be made by a multidisciplinary evaluation.