High 2-deoxy-2-[18F]fluoro-D-glucose accumulation in a case of retroperitoneal fibrosis following resection of carcinoid tumor.

Positron emission tomography (PET) using 2-deoxy-2-[18F]fluoro-D-glucose (FDG) has been shown to be a highly sensitive diagnostic tool to stage, restage, and monitor the progress of various neoplasms. A number of physiological and non-neoplastic conditions, however, also may be associated with focal accumulation of FDG and can cause false-positive results. This work reports a 52-year-old man who had marked FDG accumulation in carcinoid tumor of the distal ileum. The tumor was resected. A follow-up FDG-PET scan one and a half years later revealed intense FDG accumulation in the abdominal periaortic region, suggesting recurrent malignancy. Computerized tomography (CT) of the abdomen showed soft tissue mass surrounding the aorta. Fine-needle aspiration biopsy of the periaortic soft tissue confirmed benign retroperitoneal fibrosis. This case shows that retroperitoneal fibrosis can cause intense FDG accumulation giving false impression of malignancy. In interpretation of whole-body FDG-PET, various physiological and benign causes of FDG accumulation must be considered in order to avoid pitfalls. The authors have reviewed the literature and discussed association of carcinoid tumor and retroperitoneal fibrosis.