Incidental focal 18F-FDG uptake in the pituitary gland: clinical significance and differential diagnostic criteria

The purpose of this study was to identify the incidence and clinical significance of incidental pituitary uptake on whole-body (18)F-FDG PET/CT. We evaluated 13,145 consecutive subjects who underwent (18)F-FDG PET/CT. The final diagnosis of pathologic or physiologic uptake was based on brain MRI and follow-up PET scanning. Receiver-operating-characteristic curve analysis was performed to determine an optimal cutoff for detecting pathologic uptake. We found that 107 (0.8%) subjects showed incidental pituitary uptake. In 29 of 71 subjects with the final diagnosis, the pituitary uptake was pathologic: macroadenomas (n = 21), microadenomas (n = 5), and malignancy (n = 3). When a maximum standardized uptake value of 4.1 was used as an optimal criterion for detecting pathologic uptake, the diagnostic sensitivity, specificity, and accuracy were 96.6%, 88.1%, and 91.5%, respectively. Although incidental pituitary uptake is an unusual finding, the degree of (18)F-FDG accumulation is helpful in identifying pathologic pituitary lesions that warrant further diagnostic evaluation.