[A case of primary unknown cancer difficult to distinguish from lung cancer].

A 26-year-old man was admitted to our hospital with dyspnea, fever, and weight loss. A chest X-ray showed multiple tumor shadows, and a computed tomography (CT) scan showed swelling of the mediastinal and hilar lymph nodes, a mass in the retroperitoneum, and an embolus in the inferior vena cava. A biopsy from the left cervical lymph node revealeda poorly differentiated adenocarcinoma. Metastatic lung cancer was suspected, but in spite of the examinations, its primary site was unknown. Serum alfa-fetoprotein(AFP)was slightly elevated, but an AFP stain of the tumor was negative. The patient's respiratory failure rapidly worsened, and therefore, additional examinations could not be performed. The patient received chemotherapy with carboplatin and paclitaxel. His condition improved, but the tumor increased in size after 5 courses of chemotherapy. He received chemotherapy with docetaxel as second-line treatment, but it was not effective. The third-line chemotherapy regimen with carboplatin and gemcitabine was effective. In total, he received 7 lines of chemotherapy, and he lived for approximately 12 months since receiving the first chemotherapy regimen. After he died, we were able to perform OCT-4 immunohistochemistry on a tumor biopsy specimen from the lymph node, which came back positive for OCT-4. Therefore, we made a final diagnosis of extragonadal germ cell cancer syndrome.