MON-053 Incidental Giant Prolactinoma: A Multidisciplinary Approach

Abstract Disclosure: E. Abidor: None. M. Achkar: None. A. Agarwal: None. C. Lahoud: None. J. Zaidan: None. Introduction: Giant invasive prolactinomas present significant management challenges, particularly in elderly patients with multiple comorbidities. We present a case of an 85-year-old male whose giant prolactinoma was discovered incidentally after presenting with acute dizziness. Case Presentation: An 85-year-old male with past medical history of dyslipidemia, diverticulosis, s/p AAA repair, rosacea, eczema, and psoriasis presented to the emergency department with acute dizziness. Imaging (CT/MRI) revealed a 4.5 cm invasive pituitary macroadenoma with sellar expansion, bony destruction, and bilateral cavernous sinus invasion, encasing the internal carotid arteries. Initial diluted prolactin was markedly elevated (>4700 ng/mL). Baseline endocrine labs (free T4 1.2 ng/dL, TSH 1.07 µIU/mL, ACTH 19.8 pg/mL, AM cortisol 14.5 µg/dL) ruled out central hypothyroidism and central adrenal insufficiency. Cabergoline 0.5 mg weekly was initiated but discontinued due to psoriasis exacerbation. Bromocriptine was similarly poorly tolerated. Four months later, endoscopic transsphenoidal resection of the pituitary mass was performed, but gross total resection was not achieved due to extensive bony erosion. Postoperative prolactin remained elevated (>4700 ng/mL), with transient hyponatremia (Na 134 mEq/L) but normal AM cortisol (16.8 µg/dL) and ACTH (50.8 pg/mL). Histopathology confirmed a pituitary neuroendocrine tumor (PitNET), sparsely granulated lactotroph subtype, positive for Pit-1, prolactin, and estrogen receptor. Given persistent hyperprolactinemia, radiation therapy was considered. However, after multidisciplinary discussion involving neurosurgery, radiation oncology, and endocrinology, cabergoline was re-initiated, resulting in a substantial prolactin decline (74.1 ng/mL at three weeks, subsequently 110 ng/mL at six weeks). Follow-up MRI showed diminished residual macroadenoma within the sella and cavernous sinuses, sparing the optic apparatus. Conclusion: This case highlights the complex management of giant invasive prolactinomas. It demonstrates successful medical management after initial intolerance and surgical intervention, emphasizing personalized strategies, multidisciplinary collaboration, and the dynamic nature of treatment response. Presentation: Monday, July 14, 2025