Inflammatory myofibroblastic tumors (IMT) are a rare clinicopathological entity of yet unknown etiology and those located retroperitoneally are even rarer. Clinical outcome is unpredictable and complete surgical resection of the tumor remains the principal treatment. We report the case of a 41-year old man presented with abdominal pain. An abdominal magnetic resonance imaging scan revealed a retroperitoneal tumor located between the pancreas, stomach small curvature and big vessels. A laparotomy with biopsy was performed because the tumor was not amenable to surgical resection. Histopathological examination concluded to an IMT with overexpression of protein p53. Epstein-Barr virus and Human Herpesvirus-8 investigation was negative. Postoperative outcome was unfavorable.