[A case of pericardial diverticulum with changing size].

A 39 year-old woman with a tumor shadow in the right upper mediastinum noticed by chest x-ray examination of mass survey was presented. Chest x-ray films taken 5 times in a month in a same position showed the mass further changed in size. This result indicates the communication between the mass and pericardial cavity. Surgical extirpation was carried out and diagnosed a pericardial diverticulum.