SAT-071 - Metastatic Insulin-Secreting Neuroendocrine Carcinoma Causing Refractory Hypoglycemia.

Insulinoma is a rare pancreatic neuroendocrine tumor and the most common cause of endogenous hyperinsulinemic hypoglycemia in non-diabetic patients. The estimated annual incidence of insulinoma is 1-4 cases per million people. The vast majority of insulinoma are benign; however, approximately 5-10% are malignant, defined by metastatic disease rather than local invasion alone. We report a rare case of aggressive metastatic insulin producing neuroendocrine carcinoma in a previously healthy young adult who presented with recurrent hypoglycemia requiring repeated hospital admissions. Laboratory investigations during his first hypoglycemic attack demonstrated an elevated C-peptide levels with suppressed ketogenesis, consistent with an endogenous hyperinsulinism. Abdominal imaging identified a large epigastric mass encasing the celiac axis and superior mesenteric artery branches. Core biopsy of the mass showed a high grade poorly differentiated neuroendocrine carcinoma with small cell features (Ki-67 50%). He required aggressive medical therapy for hypoglycemia including dextrose infusion, cornstarch, diazoxide, and somatostatin analogue therapy. The tumor was deemed to not be amenable to surgery. He subsequently received 6 cycles of chemotherapy with a protocol consisting of Cisplatin and etoposide followed by external beam radiation therapy. He initially had radiographic and tumor marker response to chemotherapy, however this was followed by disease relapse with metastatic progression and recurrent hospitalizations for hypoglycemia and tumor marker elevation despite resumption of palliative chemotherapy. This case is not representative of a typical insulinoma, which is generally benign; rather, it involves a rare and highly aggressive metastatic insulin-producing neuroendocrine carcinoma. The case highlights the diagnostic approach to non-diabetic hypoglycemia and illustrates the significant challenges in managing life threatening hypoglycemia in the setting of an aggressive, metastatic neuroendocrine malignancy that is not amenable to surgical resection.

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