A 56-year-old woman was found to have a mediastinal mass on routine examination. Chest X-ray, CT scan, MRI and superior vena cavography showed a right upper mediastinal tumor invading the SVC. And it was diagnosed malignant intrathoracic goiter by histological examination by percutaneous needle biopsy. On thoracotomy and mediastinotomy, the tumor located only in the right upper mediastinum and had no relation to the cervical thyroid gland. Histological examination revealed papillary adenocarcinoma. We reported a malignant complete intrathoracic goiter and added discussion on another 12 cases seen in Japanese literature.