Clinical significance of incidental pituitary uptake on F-18 FDG PET/CT

Objectives Pituitary mass is incidentally found in 10~15% of the intracranial mass and 0.2~2.8 of 100,000 patients. The aim of this study is to identify the clinical significance of incidental pituitary uptake on F-18 FDG PET/CT.

Methods 14679 patients (male=6169, mean age: 55.5±14.1 years) were included in this study. FDG PET/CT was performed for staging or treatment evaluation of cancer (13094 patients, 89.2%) or management of non-cancerous disease (308 patients, 2.1%) or cancer screening (1277, 8.7%). Final diagnosis of incidental pituitary uptake was based on brain MRI and histological confirmation. Quantitification of the pituitary metabolic activity was obtained by using the maximum standardized uptake value (SUVmax).

Results Eighteen (0.1%) of 14679 patients had incidental uptake in pituitary area. Brain MRI was available in ten patients. In six (60%) patients, brain MRI revealed pituitary adenoma (MRI positive group) and histological evaluation confirmed in one case as pituitary adenoma. One patient MRI positive group had symptom of diabetes insipidus and underwent radiotherapy after FDG PET/CT. In four patients, MRI revealed no significant pituitary abnormalities were noted (MRI negative group). The SUVmax for pituitary uptake in MRI positive group was 8.4±2.5 and MRI negative group was 6.2±1.8. (p=0.172)

Conclusions Incidental pituitary uptake on FDG PET is rare finding. In patient with incidental pituitary FDG uptake, the incidence of pituitary adenoma on MRI is relative high (60%). Further evaluation such as brain MRI is warranted when pituitary uptake is founded on F-18 FDG PET/CT.