Suggestion of Follow-Up Period in Nonfunctioning Pituitary Incidentaloma Based on MRI Characteristics.

Background: For patients diagnosed with asymptomatic, non-functional pituitary incidentaloma (PI), periodic follow-up is generally proposed. However, the recommended follow-up period differs among existing guidelines and consensus is lacking. Thus, this study aimed to suggest follow-up periods for PI based on MRI characteristics.

Methods: Between 2007 and 2023, 245 patients who were diagnosed with PI were retrospectively assessed. Their mean clinical and neuroradiological follow-up periods were 74.2 and 27.3 months, respectively. Their baseline clinical and neuroradiological characteristics were analyzed. These 245 patients were divided into two groups: those with PI size progression and those without PI size progression. Additionally, neuroradiological features of each group were analyzed according to presumptive diagnoses of PI.

Results: PI size increased in 33 of 245 patients. For the remaining 212 patients, PI size decreased or stayed unchanged. Of the 33 patients with PI size progression, ten underwent surgery. Stalk deviation (p<0.001) and lesion enhancement (p=0.001) were significantly more observed in those with PI size progression than in those without PI size progression. MRI morphological factors were not related to changes in PI size in the presumptive Rathke's cleft cyst group. In the presumptive pituitary adenoma group, absence of tumor enhancement (p<0.001) and stalk deviation (p<0.001) were significantly associated with tumor reduction and progression, respectively.

Conclusion: Our findings support an additional guideline for patients with asymptomatic non-functional PI without stalk deviation and enhancement. For these patients, the clinical and neuroradiological follow-up periods could be reduced.