6617 A Case of Doege-Potter Syndrome With Normal IGF-II

Abstract Disclosure: A.T. Yip: None. I. Donangelo: None. Background: Doege-Potter syndrome is a rare presentation of non-islet cell tumor hypoglycemia that results from ectopic secretion of IGF-II prohormone from a solitary fibrous tumor (SFT). Case: A 57-year-old woman came to medical attention after a syncopal episode requiring hospitalization for severe hypoglycemia. She had an unremarkable brain MRI but chest CT showed a 18cm pleural based mass in the right thorax with biopsy consistent with SFT. The patient left the hospital against medical advice but had recurring events of severe hypoglycemia occurring overnight. She had resorted to taking glucose tabs nightly and had her spouse routinely wake her up at 2AM to take more glucose tabs. She required direct hospital re-admission for refractory hypoglycemia and expedited investigation and surgical intervention. Blood work revealed serum glucose 31 mg/dL (65-99 mg/dL), C-peptide <0.5 ng/mL (1.1-4.3 ng/mL), insulin<1 uU/mL (3-25 uU/mL), beta-hydroxybutarate <1.0 mg/dL (≤3.0 mg/dL), negative serum and urine sulfonylurea screen, negative insulin antibody, IGF-II 130 ng/mL (180-580 ng/mL), and IGF-I 31 ng/mL(50-317 ng/mL) which confirmed suspicion for a non-insulin mediated process although her IGF-II levels were not elevated with a IGF-II to IGF-I ratio of 4. She was placed on a continuous dextrose infusion with the rate titrated to target euglycemia. She underwent right pleural mass resection and post-operatively was liberated from the dextrose infusion without subsequent episodes of hypoglycemia. Pathology sections demonstrated a well-circumscribed tumor composed of bland spindle cells arranged in a pattern-less architecture. The tumor cells stained positively for CD34 (cytoplasmic) and STAT6 (nuclear) which were consistent with SFT. During her 3-month post-op follow up she denied any further episodes of hypoglycemia. Her follow up labs showed serum glucose 81 mg/dL (65-99 mg/dL), C-peptide 1.3 ng/mL (1.1-4.3 ng/mL), insulin 3 uU/mL (3-25 uU/mL), IGF-II 467 ng/mL (180-580 ng/mL), and IGF-I 128 ng/mL (50-317 ng/mL). Oncology recommended routine surveillance with PET CT scans. Clinical Lessons: Although rare, Doege-Potter syndrome should be on the differential diagnosis for non-insulin mediated hypoglycemia. Despite being an IGF-II mediated process, SFTs most commonly produce a high molecular weight “big” IGF-II molecule that is usually not detected by commercial laboratory assays thus leading to non-elevated levels of IGF-II, normal IGF-II:IGF-I ratios, and potential a delay in diagnosis of cases where a tumor has yet to be identified. Additionally, when IGF-II tumor immunostaining is unavailable, STAT6 serves as a highly sensitive and specific marker for SFT. This tumor generally does not have malignant potential and the associated hypoglycemia typically resolves after surgical resection of the SFT. Presentation: 6/1/2024