Prevalence and clinical significance of incidental 18F-FDG uptake in the pituitary

Background Incidental(18)F-FDG uptake in the pituitary may be detected during PET examinations. We aimed to perform a systematic review and a meta-analysis about prevalence and clinical significance of this finding. Methods A comprehensive computer literature search, using several databases, was performed until March 2020. Pooled prevalence and rate of malignancy, including 95% confidence interval values (95% CI), were calculated on a per-examination based analysis. Results Five studies (180 cases of incidental(18)F-FDG uptake in the pituitary) were included; most of the cases were further evaluated with MRI. The pooled prevalence of incidental(18)F-FDG uptake in the pituitary was 0.33% (95% CI 0.07-0.78%). Adenomas were the most frequent lesions underlying an incidental(18)F-FDG uptake in the pituitary when further evaluated with MRI (pooled prevalence: 66%; 95% CI 42-86%). The pooled rate of malignancy in cases of incidental(18)F-FDG uptake further evaluated with MRI was 13% (95%CI 3-31%). Notably, a significant heterogeneity among the selected studies was found. Of note, in the available series, there were not patients with incidental(18)F-FDG uptake in the pituitary treated with immunotherapy. Conclusions Clinicians, radiologists and nuclear medicine physicians should be aware that incidental(18)F-FDG uptake in the pituitary is an infrequent finding corresponding to benign lesions in most of the cases. Nevertheless, if the patient has normal life expectancy, MRI pituitary examination should be performed to better characterize these incidental findings due to possible clinical consequences of some pituitary incidentalomas if untreated. Further well-designed studies are needed on this topic, especially in view of the increasing frequency of immunotherapy, whose side-effects can be seen by increased(18)F-FDG uptake in the pituitary.