SAT-111 FSH+ gonadotroph adenomas have greater MRI apparent diffusion coefficients and gross total resection rates than FSH- gonadotroph adenomas

Abstract Disclosure: Y. Park: None. D. McArdle: None. F. Gaillard: None. R. Ly: None. J. King: None. A.S. Trigos: None. A. Shen: None. C.J. Yates: None. IntroductionSteroidogenic factor 1 (SF1) immunohistochemistry (IHC) has led to an increased detection of gonadotroph adenomas1 and SF1+/luteinising hormone (LH)-/follicular stimulating hormone (FSH)- gonadotroph adenomas are the most prevalent histological gonadotroph adenoma subtype.2 Clinical heterogeneity of gonadotroph adenoma has been suggested between the LH-/FSH+, LH+/FSH- and FSH+/LH+ subtypes.3 However, clinical significance of the SF1+/LH-/FSH- histological subtype is unknown. Methods: In a retrospective matched cohort study at an Australian tertiary hospital, inpatients diagnosed with pituitary tumours between 1st January 2021 and 3rd July 2024 were screened using ICD codes and an established pituitary database. One SF1+/LH-/FSH- gonadotroph adenoma was matched per other gonadotroph adenoma histological subtypes by age and sex. Pre-operative MRI was analysed for tumour volume, invasiveness, texture analysis, and apparent diffusion coefficient (ADC) values. Serial MRI at 3-6 months post-operatively and the most recent available were analyzed. Clinical (including reproductive hormones and reoperation) and IHC data were collected. Results: Of 70 patients with confirmed gonadotroph adenomas, one SF1+/LH-/FSH- gonadotroph adenoma (n=13) was matched with 13 other gonadotroph adenoma histological subtypes (SF1+/LH-/FSH+ (n=5)/SF1+/LH+/FSH- (n=4)/SF1+/LH+/FSH+ (n=4). FSH+ gonadotroph adenomas (SF1+/LH-/FSH+ and SF1+/LH+/FSH+, n=9) had higher ADC (892 [786-943] vs. 664 [592-719] mm2/s; p=0.007) and achieved more GTR (50% vs. 0%; p=0.048) compared to FSH- gonadotroph adenomas (SF1+/LH-/FSH- and SF1+/LH+/FSH-, n=14). There were no differences in invasion (Knosp grade ≥ 3 or sphenoid sinus invasion) (p=0.48) or reoperation (p=0.57) between the two groups. There were no differences in tumour volume (p=0.38), T1 intensity (p=0.43), T2 intensity (p=0.21), Knosp grade (p=0.94), sphenoid sinus invasion (p=0.74), hypopituitarism (p=0.28), use of sex hormone replacement therapy (p=0.37), estrogen receptor alpha IHC (p=0.14), Ki67 (p=0.81) and reoperation (p=0.79) across the four histological subtypes. All tumours had a suprasellar extension. On dynamic contrast-enhanced sequences, delayed (n=14/16) and heterogeneous enhancement (n=19/24) relative to normal pituitary were common. Serum LH and FSH levels were not associated with LH (p=0.51) and FSH IHC (p=0.78) respectively. Conclusions: Our small pilot study demonstrated FSH+ gonadotroph adenomas have greater MRI apparent diffusion coefficients and GTR rates than FSH- gonadotroph adenomas, however, without differences in invasion or reoperation. High ADC values have been associated with a reduced risk of recurrence4 and invasiveness5 of pituitary adenomas. Larger studies are warranted to evaluate ADC of gonadotroph adenoma histological subtypes and its potential clinical significance. Presentation: Saturday, July 12, 2025