2025 Proffered Presentations
S122: IMMUNOHISTOCHEMISTRY FOR LINEAGE SPECIFIC TRANSCRIPTION FACTORS MARKEDLY IMPROVES THE ACCURACY OF DIAGNOSIS IN PITUITARY ADENOMA
Thomas Hanks, BS; Spencer Raub, BA; Kyly Hiatt, BS; Jessica Eaton, MD; Kaity Hartl, MS, PAC; Dominic Nistal, MD; Fatima El-Ghazali, MD; Aria Jamshidi, MD; Samuel Emerson, MD, PhD; Manuel Ferreira, MD, PhD; Jacob Ruzevick, MD; University of Washington
Introduction: The current guidelines for classification of nonfunctional pituitary adenoma include immunohistochemical (IHC) staining for lineage specific transcription factors (TF). Use of IHC for anterior pituitary hormones likely underreports true rates of an individual tumor lineage in favor of overreporting of null cell tumors.
Objective: To compare our institution’s use of TF IHC to correctly identify nonfunctional pituitary adenoma lineage as compared to traditional IHC methods.
Methods: A single institution, retrospective study of 191 nonfunctional pituitary adenomas undergoing surgical resection between 2021 and 2024 was performed. Patients were included if pathology specimens had IHC for both anterior pituitary hormones and lineage specific TF.
Results: A total of 191 patients were included for study, of which 46.1% were female with an average age of 57.5 ± 14.7 years. When stained for TF, a total of 111 (58.1%), 19 (9.9%), and 35 (18.3%) tumors stained for SF-1, PIT-1, and T-PIT, respectively. A total of 16 (8.4%) patients stained for multiple TF, and 10 (5.2%) patients demonstrated no positive staining for any TF. Of the 111 positive stains for SF-1, 36 (32.4%) showed no positive staining for anterior pituitary hormones. For the 19 tumors who stained positive for PIT-1, two (10.5%) showed no positive staining for anterior pituitary hormones. For the 35 tumors who stained positive for TPIT, 7 (20%) were negative on staining for anterior pituitary hormones. Overall, of the 165 patients who had positive staining for a single TF, 45 (27.3%) did not show IHC staining for anterior pituitary hormones and thus would have been previously classified as null cell pituitary adenomas. Use of IHC for identification of lineage specific TF significantly improves the rate of correct pathological classification of pituitary tumors and decreases the rate of diagnosis of null cell pituitary adenomas to 5.2%.
Conclusion: The use of IHC for identification of lineage specific TF markedly improves the accuracy of correct pathological diagnosis of pituitary adenomas and allows for more accurate counseling of patients regarding tumor subtype and prognosis.