[Retroperitoneal metastasis from testicular tumor: Mature teratoma with adenocarcinomatous transformation].

A 41-year-old patient, with a medical history of embryonal carcinoma treated by orchidectomy at the age of 27, presented with abdominal pain. Serum alphafetoprotein, β-HCG and CEA levels were normal. MRI showed a cystic retroperitoneal lesion with septation, measuring 20cm. He underwent a surgical resection. Histology revealed an adenocarcinoma arising on a mature multitissular teratoma.