RESUMO
Primary retroperitoneal extra-organ tumors (PRET) are a relatively rare group of diverse neoplasms. They are classified in three main groups according to their histogenesis: PRET from mesodermal origin, from ectodermal origin and from embryonic remnants. Most of PRET are malignant, a the most frequent malignant PRET are soft tissue sarcomas. Because of their specific localization PRETs grow silently for a relatively long period and are often considerably large at the time of diagnosis. These tumors usually have no specific symptoms. Computerized tomography and magnetic resonance imaging are the most useful methods in the diagnosis of PRET. Surgery is the only effective treatment of PRET with exclusion of some histologic types as lymphoma and malignant germ cell tumors. One of the most specific characters of PRET is their great tendency to recur locally, which is explained not only by their biological characteristics but the difficulties of accomplishing a radical resection. For the malignant PRET, especially the retroperitoneal soft tissue sarcomas, no adjuvant therapy has proved to be beneficial on survival.