PMON105 Giant Growth Hormone (GH)-Secreting Pituitary Tumor with Massive Sphenoid Sinus Invasion and Spontaneous Cerebrospinal Fluid (CSF) Leak: A Case Report

INTRODUCTION: Giant pituitary tumor, defined as >4cm, comprise 6-10% of all pituitary tumors. Giant GH-secreting pituitary tumors are rare and difficult to treat. They typically invade surrounding structures ​such as the cavernous sinus, making ​complete resection challenging or impossible. This report highlights a case of giant GH-secreting pituitary tumor with an unusual clinical presentation.CLINICAL CASE: A 56 Y/O male with hypertension, cardiomyopathy, obesity, and OSA presented to the ER with stroke-like symptoms. Brain CT and MRI revealed small acute to subacute infarcts within the left occipital, left frontal, right frontal, right parietal areas, and right cerebellum. An incidental finding was a 4.3 cm T2 hyperintense enhancing mass centered within the skull base with involvement of the sella, extension into bilateral cavernous sinuses, clivus, encasement of bilateral carotid arteries, and invasion through the sphenoid sinus into the nasopharyngeal space resulting in a preoperative CSF. He was overtly acromegalic with coarse facial features, prominent frontal bossing, early prognathism, and macroglossia. Hands and feet were enlarged, but non-edematous. Visual field testing was normal. Laboratory values: IGF-1, 317 ng/mL (NL <170): GH, 4 ng/ml (NL<10); prolactin, 17.6 ng/mL (NL 2.5-17.4); total testosterone, 11 ng/dL (NL 130-810); free testosterone, 2 pg/dL (NL 36-146). ACTH stimulation produced a normal cortisol response. Test for AIP gene mutation was negative. Emergent packing of the CSF leak site was done. He underwent trans-sphenoidal (TSS) debulking of the tumor along with reconstruction of the ​skull base and repair of CSF leak. Postoperatively, IGF-1 level decreased to 216 ng/mL. Immunohistochemical stains of the tumor were strongly positive for GH and somatostatin receptor type2 (SSTR2). Three weeks postoperatively, IGF-1 increased to 482 ng/mL. IGF-1 level decreased to 326 ng/mL after 3 doses of lanreotide 90 mg/month. He will be now monitored on 120 mg/month. Currently, he requires only testosterone replacement. CONCLUSION: This patient had the unique presentation of florid acromegaly and CSF leak mainly related to his delay in seeking medical care. Absence of visual defects has been noted in only 15% of reported patients with giant GH-secreting adenomas. Massive replacement of the sphenoid sinus by a giant pituitary tumor causing a CSF leak with invasion into the ​cavernous sinuses and clivus has been rarely reported. Trans-sphenoidal resection is the preferred first-line treatment for patients with acromegaly. The remission rate decreases and can reach almost 0% for giant GH-secreting tumors. Somatostatin receptor analogs (SRA) are the preferred first-line pharmacological treatment as an adjuvant therapy for residual tumor. Our patient likely will need continued SRA and potentially other modalities to control acromegaly due to unresectable tumor anatomy. This case also highlights the complications of delayed detection and benefits of extensive TSS surgical resection with the goal to enhance his response to SRA. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.