Solitary fibrous tumors (SFTs), are a group of rare, spindle-cell derived fibrous neoplasms most commonly found in the thoracic (pleural) cavity (80%).However, it has been described that SFTs can affect a wide range of anatomic sites outside the pleura, including retroperitoneum, meningeal, nasal cavity and others (20%).Solitary fibrous tumors are usually described in patients between 40 and 70 years of age, and are primarily benign.We present the case of a 27-year-old male with an incidental finding of a retroperitoneal mass, reported during a routine CT-scan for a pneumonia follow-up, its surgical resection and histopathological findings.