Incidental pituitary uptake on whole-body 18F-FDG PET/CT: a multicentre study

The purpose of this study was to determine the incidence of incidental pituitary uptake on whole-body 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) and to investigate its clinical significance.

The files of 40,967 patients who underwent whole-body FDG PET/CT were retrospectively reviewed. Quantification of pituitary metabolic activity was obtained by using the maximum standardized uptake value (SUVmax). Hormone assays and pituitary MRIs were performed to assess pituitary lesions.

Focally increased pituitary FDG uptake on PET/CT was found in 30 of 40,967 patients, accounting for an incidence of 0.073%. The mean SUVmax of 30 patients was 8.9±6.6 (range: 3.2-32.6). Histological diagnosis was obtained in three patients and included two growth hormone-secreting adenomas and one non-functioning adenoma. Hormone assays were performed on serum samples from 11 patients, 2 of whom were shown to have hypersecretion of pituitary hormone. MRI was performed on 19 patients. Abnormal MRI findings suggesting a pituitary mass were found in 18 of 19 cases (94.7%). The mean SUV(max) calculated without correction for partial volume effect for macroadenomas was significantly higher than the SUVmax for microadenomas (11.5±8.4 vs 4.8±1.3; p<0.05). There were no cases diagnosed with metastasis to the pituitary gland during clinical follow-up.

Incidental pituitary FDG uptake was a very rare finding. Cases with incidental pituitary FDG uptake were diagnosed primarily with clinically non-functioning adenomas, and there were also a few functioning adenomas. Further evaluations, including hormone assays and pituitary MRI, are warranted when pituitary uptake is found on FDG PET/CT.