THU077 Differences In Clinicopathological Features Of Acidophil Stem Cell Adenomas Compared To Other Subtypes Of Acromegaly: A Retrospective Study

Disclosure: K.C. Yuen: Advisory Board Member; Self; Novo Nordisk, Ascendis, Corcept Therapeutics, Ipsen, Amryt, Strongbridge, Crinetics, Recordati, Xeris. Grant Recipient; Self; Corcept Therapeutics, Crinetics, Ascendis, Amryt. Speaker; Self; Corcept Therapeutics, Novo Nordisk, Recordati. E. Smith: None. F. Bernabe: None. J.M. Eschbacher: None. M. Rodriguez: None. A.S. Little: None. Background: Acidophil stem cell adenomas (ASCAs) are tumors derived from a precursor of somatotrophs and lactotrophs. Often presenting clinically like prolactinomas that respond to dopamine agonist therapy, some may also present with subtle clinical symptoms and biochemical features of acromegaly. Because ASCAs are so rare, their clinicopathological features have not been well-studied. Aims: Clinicopathological features of ASCAs were analyzed and compared with mixed somatotroph-lactotroph adenomas (MSLAs), mammosomatotroph adenomas (MSAs) and pure somatotroph adenomas (PSAs). Methods: We retrospectively reviewed the medical records of acromegaly patients from a single institution presenting from 2001 to 2022. All growth hormone-secreting adenomas were categorized into ASCAs, MSLAs, MSAs and PSAs based on their histopathological findings in surgically treated patients, and their pre- (preop) and post-operative (postop) clinical data were analyzed. Results: Among 135 patients within this cohort, ASCAs, MLSAs, MSAs and PSAs accounted for 21 (15.5%), 11 (8.1%), 59 (43.7%) and 44 (32.6%) cases, respectively. ASCA patients were younger (mean age ASCA: 48.6 vs MLSA 56.5, MSA 59.0, PSA 63.4 years; P < 0.05), had higher preop prolactin levels (ASCA: 1190 ± 639.0 vs MSLA: 44.9 ± 23.2, MSA: 39.7 ± 6.8, PSA: 23.8 ± 5.5 µg/L; P < 0.01), had higher rates of MIB-1 labeling indices (ASCA 76.2% vs MSLA 39.0%, MSA 45.5%, PSA 43.2%; P < 0.05) and preop visual field defect (VFD) (ASCA 32.3% vs MSLA 13.6%, MSA 27.3%, PSA 29.6%; P < 0.05), and had lower rates of preop hypertension (HTN) (ASCA 14.3% vs MSLA 52.5%, MSA 36.4%, PSA 31.8%; P < 0.05) and diabetes mellitus (DM) (ASCA 14.3% vs MSLA 27.2%, MSA 54.5%, PSA 20.5%; P < 0.05). ASCA tumors were larger than MSAs (2.3 ± 1.0 vs 1.6 ± 0.7 cm; P < 0.01), but comparable to MSLAs and PSAs. Rates of cavernous sinus invasion and preop GH levels were similar between groups. Postop GH levels were higher in ASCA (8.6 ± 5.3 µg/L) compared to MSLAs (2.4 ± 0.5 µg/L) and MSAs (1.1 ± 0.7 µg/L) (P < 0.05). ASCA preop IGF-I levels were lower than PSA (ASCA: 466.7 ± 118.5 vs PSA: 803.7 ± 56.5 µg/L; P < 0.05), while postop IGF-I levels were comparable to MLSAs, MSAs and PSAs. ASCAs also had lower postop remission rates compared to MLSAs, MSAs and PSAs (ASCA 19.0% vs MLSA 45.5%, MSA 38.6% and PSA 54.2%; P < 0.05). Most ASCA (85.7%), MLSA (81.4%), MSA (100%) and PSA (77.2%) patients underwent one surgery and more ASCA (23.8%), MLSA (25.4%) and PSA (22.7%) patients underwent radiation therapy than MSA (9.1%) patients. Conclusions: Our data demonstrated important insights into the differences of clinicopathological features of ASCAs compared to other acromegaly subtypes. Notably, ASCAs occurred in younger patients, had larger and more aggressive tumors, had lower postop remission rates and had higher VFD rates. In addition, ASCAs had higher rates of preop hyperprolactinemia and lower rates of preop HTN and DM. Presentation: Thursday, June 15, 2023