Incidental detection of rare mesenteric inflammatory pseudotumor by (18)F-FDG PET

A 60 years old asymptomatic male underwent fluorine-18 fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) for his medical check-up, and abnormal (18)F-FDG uptake was observed in the retroperitoneum. The maximum standardized uptake value (SUV (max)) was 5.2. Based on CT, MRI and (18)F-FDG PET findings, the differential diagnosis included specific or non-specific inflammatory change, malignant lymphoma, trauma, gastrointestinal stromal tumor and soft-tissue sarcoma. Tumor resection was performed, and the histopathological finding was an inflammatory pseudotumor (IPT) originating at the mesentery in the retropetonium. After two years and eight months from his initial operation, recurrent IPT was detected by (18)F-FDG PET for follow-up, although he was asymptomatic. The IPT could be of traumatic origin since the patient suffered a severe abdominal trauma 6 months before. A mesenteric IPT is very rare, and to our knowledge, this is the first case report of (18)F-FDG PET detecting a mesenteric IPT. In conclusion, when abnormal high (18)F-FDG uptake is observed in the mesentery incidentally in clinical routine examination, IPT should be included as one of the differential diagnoses. (18)F-FDG may be useful in detecting local recurrence and follow-up after operation.