[Primary retroperitoneal tumors in adults]

Primary retroperitoneal tumors are rare and most of the time malignant. Because of the large space in which they grow, they are often discovered lately as they are large. CT and MR are the imaging techniques of choice for the primary diagnosis and the follow up of these tumors. Multiplanar reconstructions , signal and density resolution help for the nature diagnosis. The examinations allowed to find associated signs that helps also for the right diagnosis. The purpose of this paper is to answer a serie of questions: Is the mass in the retroperitoneal space? Are they imaging signs that helps for the diagnosis of nature? Are they associated signs that helps for the diagnosis of nature? What are the most common diagnosis? Is there any place for percutaneous biopsies? What is the role of imaging in the follow up? Are there any other processes that can mimic retroperitoneal tumors?