Cystic malignant teratoma with early recurrence after intraoperative spillage.

Teratoma with malignant transformation, defined as germ cell tumors with a malignant component of nongerm cell tumors, such as sarcomas and carcinomas, is rarely seen in the mediastinum. A rare case of the mediastinal mature cystic teratoma with focal gastrointestinal adenocarcinoma is described in this report. The patient underwent a video-assisted thoracoscopic surgery for tumor resection. Intraoperatively, the cystic tumor was ruptured due to dense adhesion. The rapid tumor dissemination was postoperatively noted. Careful and complete resection with the cyst wall of the mediastinal mature cystic teratoma intact is necessary to avoid a risk of relapse from a potentially malignant component.