Primary retroperitoneal germ cell tumor should be diagnosed pathologically, and immunohistochemistry (IHC) plays a vital role in its diagnosis and differential diagnosis.[13] Among the IHC indicators, the positive expression of placental alkaline phosphatase (PLAP), CD117, and Octamer-binding transcription factor 3/4 (OCT3/4) is considered to show important diagnostic value for the diagnosis of seminomas.[13] Similarly, in our female case, all the above 3 IHC indicators were positively expressed, which were in consistent with the characteristics of dysgerminoma. The gene discussed is POU5F1; the disease is dysgerminoma.