Germ cell tumors with somatic-type solid malignancy are mostly attributed to the malignant transformation of teratomas. Herein, we describe the case of a 41-year-old man with mediastinal yolk sac tumor who presented with adenocarcinoma in nodal metastases. Computed tomography revealed enlarged subcarinal lymph nodes and an anterior mediastinal tumor, which was diagnosed as a yolk sac tumor by percutaneous biopsy. The remaining tumor was resected after chemotherapy. No viable cells were observed in the primary tumor; however, adenocarcinoma was detected in the subcarinal lymph nodes. Mediastinal yolk sac tumors can be associated with metastatic adenocarcinoma in locoregional lymph nodes.
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