Characterization of Gonadotroph Pituitary Adenomas Based on the Recent 2017 WHO Pituitary Tumor Classification

Abstract

Abstract Introduction: More than 20% of pituitary adenomas are nonfunctional, the majority of which are of gonadotroph origin. Whereas previously, immunohistochemistry of pituitary hormones was used to classify adenoma subtypes, in 2017 the World Health Organization (WHO) reclassified pituitary adenomas using transcription factor expression in addition to immunohistochemistry. With this change, clinically nonfunctional gonadotroph adenomas can be distinguished among: (1) those staining for the transcription factor SF-1 and gonadotropins FSH and/or LH (FSH/LH+), (2) those that stain for SF-1 but not for FSH or LH (FSH/LH- SF1+), and (3) true null cell adenomas. It is unclear whether these three subgroups behave similarly clinically, or if they have distinct manifestations or outcomes. Our aim was to characterize these subgroups in regard to tumor size, recurrence and pituitary insufficiency. Methods: In a retrospective chart review, 71 patients from 2017-2020 who presented to the hospital for transsphenoidal resection of clinically nonfunctioning pituitary adenomas were reviewed. All patients with pituitary adenomas that stained positive for SF-1 and negative for T-PIT and PIT-1, and tumors that were negative for all three transcription factors were evaluated. Those lacking clinical data were excluded. Clinical characteristics examined include: demographics, tumor size, invasion of cavernous sinus, and hormone deficiencies. Results: Of the 71 pituitary tumors, 45% (n=32) stained positive for the beta subunit FSH and/or LH (FSH/LH+) and SF-1, 44% (n=31) stained for SF-1 with negative pituitary hormone stains (FSH/LH- SF1+), and 11% (n=8) were negative for all transcription factors and hormones (true null). All tumors were macroadenomas (>1 cm). While there were >50% males in the FSH/LH+ and FSH/LH- SF1+ groups, in the true null group only 25% of patients were male. Most patients were >50 years old in all 3 groups (81% FSH/LH+, 75% FSH/LH- SF1+, 88% true null). The prevalence of cavernous sinus involvement was 36% in both groups that stained for SF-1, but was 62% in the true null group. Both SF-1+ groups had similar tumor sizes and prevalence of panhypopituitarism (15-21%), but there were more episodes of recurrence since last known follow up in the FSH/LH- SF1+ group (20%), compared to FSH/LH+ tumors (7%). The true null group had ≥50% rates for both panhypopituitarism and recurrence. Conclusions: In this study, we highlighted the category of FSH/LH- SF1+ gonadotroph adenomas and compared these to FSH/LH+ and true null cell tumors. Based on clinical features, FSH/LH- SF1+ gonadotroph adenomas are similar to FSH/LH+ staining pituitary adenomas in regard to age, sex, size, and degree of cavernous sinus invasion, although there were more recurrences in the FSH/LH- SF1+ group. Though less common, our cohort suggests more aggressive tendencies in the true null group compared to SF-1 staining tumors.