We report on a 26-year old female patient with thoracic pain and dyspnea, in whom a large tumorous mass in the anterior mediastinum with a pleural effusion was diagnosed by computed tomography and magnetic resonance imaging. After rapid progression of tumor growth and detection of malignant cells within the pleural effusion operative intervention including resection of the tumor was performed. Histologic examination of the tumor revealed the typical morphology of a large mediastinal choriocarcinoma. The excessively high hCG-levels returned to normal values post-operatively. A thorough history making revealed an ectopic pregnancy which had made unilateral salpingectomy necessary. Although primary histologic examination of the tubarian tissue had shown no malignancy, a secondary look revealed a choriocarcinoma with identical histological features compared to the mediastinal tumor. Thus, final diagnosis of a mediastinal metastasis of a tubarian choriocarcinoma in ectopic pregnancy was made. We discuss this extremely rare disease and provide a short overview of the literature.