[Retroperitoneal schwannoma mimicking colorectal cancer metastases: a false positive result report.]

Introduction: schwannomas are benign and common soft tissue tumors. They are usually asymptomatic and are discovered for other reasons.

Materials: we present the case of an 82-year-old male patient with a recent diagnosis of moderately differentiated adenocarcinoma of the colon and a hypermetabolic periaortic nodule as an incidental finding.

Results: percutaneous biopsy of the periaortic nodule confirmed the diagnosis of schwannoma. At one year of follow-up, growth of the schwannoma has been demonstrated. There are no signs of progression of his oncological disease.

Conclusions: schwannomas are benign tumors, rarely found in the retroperitoneum and can be sources of false-positive positron emission tomography results.