18F-FDG uptake in intraductal tubulopapillary neoplasm of the pancreas.

We report a 74-year-old man with intraductal tubulopapillary neoplasm (ITPN), a rare primary intraductal neoplasm of the pancreas. Focal intense uptake of 18F-FDG was seen on the initial PET, corresponding to a pancreatic mass. Although the patient had no treatment, the uptake was mild to moderate on a second PET performed about 1 month later. The tumor was resected, with the final diagnosis of ITPN with an associated invasive carcinoma. Clinicians should be aware that decreased uptake of FDG during the follow-up period without treatment can occur even in malignant tumors.