A 54-year-old man with primary mediastinum choriocarcinoma

Primary mediastinum choriocarcinoma, an extragonadal germ cell tumor, is a rare malignant tumor that is more common in men. We present a case of primary mediastinum choriocarcinoma in a male patient who initially presented with gynecomastia and progressed to superior vena cava syndrome. Both surgical biopsy and pathologic diagnosis were challenging. After standard induction chemotherapy, the resected tumor underwent squamous cell transformation, which has rarely been reported in cases of choriocarcinoma. His critical condition was resolved using induction chemotherapy with a combination of bleomycin, etoposide, and cisplatin, followed by resection of the residual tumor. However, tumor recurrence occurred 9 months later, and he was treated with salvage radiotherapy and chemotherapy. This was a rare and challenging case from the aspects of initial approaches, pathologic differential diagnosis, and different treatment modalities.