Objective  To investigate the clinicopathological features and diagnosis of high-risk pituitary adenomas.

  Methods  From June 2017 to September 2020, the clinicopathological and follow-up data of 24 patients diagnosed with high-risk pituitary adenomas from Peking University International Hospital were collected, and morphological observation, immunohistochemical (IHC) staining, and sequencing were performed.

  Results  Of the enrolled patients, 14 were male and 10 were female, with an onset age ranging from 28 to 68 years and a median age of 45.4 years. Clinically, mass effects and symptoms caused by inappropriate hormone secretion were commonly presented. Tumor size ranged from 0.7 cm to 4.8 cm; 12 cases were invasive adenoma according to maging examinations. Tumor type was determined by IHC staining combined with serum hormone level and clinical features. Four cases were diagnosed as sparsely granulated somatotroph adenomas, 12 were silent corticotroph adenomas, 6 were lactotroph macroadenomas in men, and 2 were plurihormonal PIT-1 positive adenomas. One case had GNAS mutation. Follow-up data were available for 14 patients, of whom 2 developed local recurrence and one died.

  Conclusions  The exact diagnosis of high-risk pituitary adenoma should be based on IHC, serum hormone level assessment, and clinical symptoms. The risk of recurrence and more-aggressive behaviour should be considered by surgeons and patients.