Retroperitoneal Extragonadal Germ Cell Tumors
Extragonadal germ cell tumor (EGGCT) represents 5–10% of germ cell tumors and frequently occurs in mediastinum, retroperitoneum, pineal gland, or sacral area. EGGCTs are mostly benign, such as teratoma and yolk sac tumor. Typical malignant EGGCTs mainly include malignant teratoma and embryonal carcinoma, while seminoma and choriocarcinoma are rarely seen. Less than 1000 cases of primary retroperitoneal seminoma have been described worldwide; as a subtype of EGGCT, it commonly occurs in young adult aged 30–50 years.