Inflammatory myofibroblastic tumors (IMT) were previously included in the "inflammatory pseudotumors" family, but have emerged as a distinct entity recently. The management of IMT may be challenging due to its intermediate malignant potential. We present a case of a young patient with an asymptomatic retroperitoneal mass with some imaging findings that could point to the IMT diagnosis pre-operatively. After two failed attempts to fully characterize the lesion by percutaneous and surgical biopsy, surgical resection was conducted and the final diagnosis was achieved.