SUN-285 A Recurrent Middle Ear Neuroendocrine Tumor Leading to Metastatic Disease and Fatal Hypoglycemia

Abstract Disclosure: M. Kanwal: None. I. Garg: None. B. Tawfik: None. K.S. SantaCruz: None. T.M. Robinson: None. L. Blacklock: None. A.N. Hosford: None. P.L. Kapsner: None. C.M. Lovato: None. Introduction: Neuroendocrine tumors (NETs) are rare tumors originating from neural crest and epithelial cells. The most common locations include the gastrointestinal tract and lungs. NETs of the middle ear are very rare, accounting for less than 2% of middle and inner ear neoplasms. They exhibit neuroendocrine differentiation and can demonstrate both glandular and neuroendocrine morphologies. Middle ear neuroendocrine adenoma is usually a benign, locally nonaggressive tumor. In rare cases, there can be regional and/or distant metastasis.Clinical Case: The patient is a 73-year-old male with a history of a left middle ear NET involving the temporal bone with multiple recurrences with surgical removal of the tumor initially 30 years prior. He required additional resections 17 and 23 years, respectively, after the initial surgery. Pathology from the initial and most recent surgeries showed an infiltrative tumor that stained positive for chromogranin and synaptophysin consistent with a neuroendocrine adenoma. He had interval growth of the tumor one year ago, which was treated with radiation. He then presented to our institution 10 months later after a syncopal episode. He was noted to have a glucose of 35 mg/dL (n 60-100 mg/dL) requiring a dextrose drip. MRI of the brain showed increased size of the left middle ear NET with vasogenic edema. He was started on dexamethasone. CT scan chest, abdomen, and pelvis showed extensive lung, liver, and bone metastases. He continued to experience hypoglycemia with lab data showing whole blood glucose 35 mg/dL with inappropriately elevated c-peptide 6.2 ng/mL (n 1.1-4.4 ng/ml), insulin 22.4 UIU/ml (n 2.6-24.9 UIU/mL), and proinsulin 45.5 pmol/L (n <7.2 pmol/L). Beta hydroxybutyrate was <0.1 mmol/L. Sulfonylurea screen and insulin antibodies were negative. Gallium-68 DOTATATE PET/CT showed diffuse somatostatin receptor positive disease with intracranial, cranial, and extracranial involvement, concordant with metastatic sites seen on CT. He underwent biopsy of one of the liver lesions, which stained positive for synaptophysin, chromogranin, and PAX6. Based on the Ki-67 index of 40-50% and morphology, this was characterized as a well-differentiated NET, grade 3. The patient was started on octreotide with initial improvement in hypoglycemic episodes. However, hypoglycemia recurred, and despite treatment with maximum doses of octreotide, dextrose drip, and dexamethasone, the patient’s medical condition steadily declined and he passed away due to complications of hypoglycemia.Conclusion: This is a case of a recurrent NET of the middle ear that transformed to a more aggressive tumor with distant metastases and complicated by hypoglycemia due to ectopic insulin secretion. Clinicians should be aware of this rare clinical presentation and consider further investigation with specialized imaging and biochemical testing in patients with these types of NETs. Presentation: Sunday, July 13, 2025