Appendix Insulin Secreting Neuroendocrine Tumor in a Diabetic Patient: A Challenging Diagnosis

Introduction: Tumor-induced hypoglycemia is a rare entity and it is mainly due to pancreatic insulinomas. Non-islet cell tumor hypoglycemia is really exceptional and ectopic insulin secretion has been previously suggested. Case Presentation: A 79 year-old type 2 diabetic man, after over 30 years of poorly controlled diabetes, observed an unexplained improving of glycemic control with recurrent hypoglycemia. He progressively reduced insulin doses, till suspension, with persistent frequent hypoglycemia. A fasting test documented symptomatic hypoglycemia with un appropriated elevated insulin and C-peptide. CT scan and endoscopic ultrasound did not reveal any pancreatic lesion. A Ga68-Dotanoc showed a focal pathological right pelvic uptake, corresponding to an oval enhancing lesion at the targeted CT images. The patient was submitted to surgical excision of that mass, revealing an appendix neuro endocrine well differentiated tumor with lymph nodes metastasis, showing partial insulin immunohistochemistry staining. After surgery no other hypoglycemic events were documented; to control diabetes insulin therapy needed to be reintroduced. Conclusion: Extra-pancreatic insulin secreting tumors are very rare and their diagnosis in diabetic patients can be challenging. This case addresses the diagnosis and treatment of this rare entity reporting, to our knowledge, the first case of ectopic insulinoma, arising from appendix.