Discovery of a Non-Secreting Pancreatic Neuroendocrine Tumor Mimicking Insulinoma in MEN1: A Novel Diagnostic Challenge with Atypical Biochemical and Genetic Profiles and a review of literature of pNETs etiologies

This case report presents the first documented instance of a non-secreting pancreatic neuroendocrine tumor mimicking insulinoma in a 42-year-old male with Multiple Endocrine Neoplasia Type 1 (MEN1). The patient exhibited recurrent episodes of severe fasting hypoglycemia, typically indicative of insulinoma. However, biochemical tests revealed normal insulin and C-peptide levels, contradicting the usual biochemical signature of functional pNETs. Imaging confirmed the presence of a pancreatic mass, but further investigations failed to demonstrate hormone secretion. Genetic analysis revealed a novel MEN1 gene mutation, suggesting a potential link between this mutation and the atypical behavior of the neuroendocrine tumor. Despite the absence of typical insulinoma markers, surgical resection of the tumor resulted in complete resolution of hypoglycemia, confirming the tumor's role in the patient’s symptoms. This case shows that non-secreting neuroendocrine tumors in MEN1 can clinically mimic functional tumors. This calls for a reconsideration of current diagnostic criteria in MEN1 and may prompt future investigations into the topic.