Objective: To describe a case of retroperitoneal mature teratoma presenting as metastasis of a testicular mixed germ cell tumor in a thirty year old man who had lumbar and abdominal pain and mass sensation in the left hemiabdomen.
Methods: Abdominal ultrasound and thoracic-abdominal-pelvic CT multidetector scan were performed, and then after a Doppler ultrasound study of the testicles. Surgical treatment was performed: orchiectomy and retroperitoneal lesion resection.
Results: Imaging studies showed a big cystic lesion in the left retroperitoneal space, 13 × 12 × 11 cm, well defined, with thin septa, displacing the kidney; and a solid-cystic 4 cm left testicular tumor, with multiple septa, solid poles and arterial flows with low resistances. Thoracic extension study did not show any finding. The histopathologic results of the orchiectomy and retroperitoneal resection pieces were, respectively, testicular mixed germ cell tumor (seminoma, with intratubular seminoma foci and teratoma) and mature cystic teratoma.
Conclusions: Germ cell tumors derive from multipotencial cells with a large capacity of differentiation, and the nodal paraaortic chains are a natural way of dissemination of these neoplasms. Because of that, in the presence of a retroperitoneal lesion in a young patient we have to rule out testicular tumor metastasis. The retroperitoneal mature cystic teratoma must be considered as a lesion with malignant potential.