DUODENAL DIVERTICULUM PRESENTING AS A HYPERMETABOLIC MASS ON F18-FDG PET/CT

Abstract

Background: The use of fluorine-18 positron emission tomography with computed axial tomography (F-18 FDG PET/CT) is increasing in this country. This modality has shown to be an accurate test for the diagnosis and staging of various primary and metastatic malignancies to include colorectal carcinoma. Although false positives can be seen with various non-malignant processes, including infectious and inflammatory conditions, duodenal diverticuli causing false positive uptake on PET/CT has not yet been described in the literature. We report the first case report of this finding. Case: The patient was an 80-year-old woman with a history of stage I breast cancer status post modified mastectomy and tamoxifen treatment for 5 years. She was felt to be in remission when a routine blood test showed mild elevation in alkaline phosphatase. After initial work up, an F-18 FDG PET/CT was performed to further evaluate this finding, which showed a focus of abnormal radiotracer accumulation adjacent to the duodenal sweep with a delayed standardized uptake value (SUV-m) of 7.10. This focus of activity corresponded to a round 3 cm lesion on CT. As the PET/CT findings were suggestive of a neoplasm, further endoscopic evaluation with an EGD and EUS was performed. EGD using a front viewing scope showed no abnormalities in the duodenum. The EUS confirmed a 2.8 by 3.0 cm hypoechoic, well-circumscribed, fluid filled, cystic lesion adjacent to the duodenal sweep corresponding to the finding on PET/CT. On review of this area with the side-viewing camera on EUS, a duodenal diverticulum was identified which matched these findings. Discussion: PET/CT is becoming more commonly used for various malignancies. Although it is a very sensitive imaging test for hypermetabolic malignancies, there are several reported false positives, especially with infectious and inflammatory processes which utilize glucose metabolism. To date, there has not been a report of false postive F-18 FDG uptake within a duodenal diverticulum. Given that duodenal diverticulum are relatively common, it may be important to consider it as a possible source of false positives by endoscopist who evaluate these patients Conclusion: Duodenal diverticului are common and typically asymptomatic. They may be a source of false positive F-18 FDG PET/CT scans. Endoscopists need to become more familiar with this possible source of abnormal PET findings as this modality becomes more widespread in the evaluation of oncology patients.