Introduction: Pancreatic neuroendocrine tumors (PNETs) are rare, comprising less than 3% of all pancreatic neoplasms. These tumors are broadly classified as functioning or nonfunctioning. Insulinoma is the most common functioning PNET. Non-functioning PNETs often present significant diagnostic issues and may be misdiagnosed as pancreatic adenocarcinoma, especially when immunohistochemical evaluation is omitted during histological examination. We describe a case of metastatic insulinoma that was misdiagnosed as a poorly differentiated pancreatic adenocarcinoma. Case: A 65-year-old female first presented to a private hospital in 2023 with obstructive jaundice and was found to have a pancreatic head lesion that was causing biliary obstruction. As a result, a biliary stent was placed. She underwent aortocaval lymph node biopsy, and the result showed poorly differentiated pancreatic adenocarcinoma. Nonetheless, she refused surgical and oncological intervention. Even so, she remained clinically stable and maintained good functional status for 2 years. In 2025, she presented to Hospital Canselor Tuanku Muhriz with recurrent hypoglycemia fulfilling Whipple’s triad. The unexpectedly indolent clinical course prompted reassessment of the initial diagnosis. Biochemical evaluation confirmed endogenous hyperinsulinemic hypoglycemia, with inappropriately elevated insulin (11.03 µIU/mL) and C-peptide levels (1,089 pmol/L). Computer tomography of the abdomen revealed multiple hepatic lesions and progressive lymphadenopathy, suggestive of metastatic disease. Re-evaluation of the initial histopathological specimen showed a well-differentiated neuroendocrine tumor (Grade 1, Ki-67 ~2%). Hence, the diagnosis was revised to metastatic insulinoma. She was referred to the hepatobiliary surgical team for surgical debulking, but the procedure was deemed highrisk and likely to have high mortality due to the extent of the disease. She was managed with diazoxide and longacting somatostatin analogues for glycemic control. Conclusion This case highlights the critical importance of diagnostic vigilance when evaluating pancreatic neoplasms. Persistent or unexplained clinical courses, especially when endocrine symptoms arise, should prompt thorough reassessment. Immunohistochemical confirmation is essential to avoid misdiagnosis and ensure optimal patient management.
Adenocarcinoma ; Insulinoma ; Pancreatic Neoplasms