Resection of a ruptured mature cystic teratoma diagnosed two years after the onset of perforation.

Perforated cystic teratomas are rare. Our patient was a 16-year-old female who presented with severe chest pain two years ago. A right-sided pleural effusion was accidentally detected by chest radiography performed at her school. Computed tomography revealed a high density area with multiple small, thickened, lobulated lesions and a low density area with pleural effusion adjacent to a thinned wall. Pathognomonic inhomogeneous computed tomography findings led to an accurate diagnosis of a mature teratoma that had ruptured long before presentation. Thoracoscopic resection was performed, and the final histological diagnosis was a mature teratoma with partial rupture.