ABSTRACT
Primary mediastinal choriocarcinoma is an extremely rare extragonadal germ cell malignancy. A 58-year-old male presented with a lung mass, which was incidentally discovered during a periodic medical checkup. Percutaneous needle biopsy showed poorly differentiated carcinoma with large pleomorphic morphology. After the patient underwent right upper lobectomy and lymphadenectomy, the final diagnosis was choriocarcinoma. The patient received four sequential cycles of BEP chemotherapy (bleomycin, etoposide, cisplatin). After completion of BEP chemotherapy, follow-up positron emission tomography (PET) showed a complete metabolic response. Although the mediastinum is one of the most common primary sites of extragonadal germ cell tumors, primary mediastinal choriocarcinoma is liable to be misdiagnosed as lung cancer or Hodgkin lymphoma. Notably, large cell carcinoma of the lung can be confused with choriocarcinoma even after percutaneous needle biopsy. We report a case of primary mediastinal choriocarcinoma mimicking large cell carcinoma of the lung in a male patient in his 50s.