A 55-year-old woman with a large polyhormonal neuroendocrine tumor with unusual pathology is described. The patient presented with intermittent neuroglycopenic symptoms between more protracted asymptomatic periods occurring over the preceding 4 years. During a diagnostic 72-hour inpatient fast, she exhibited hypoglycemia at 70 hours after initiation. On computed tomography scan, a 6-cm mass was identified at the pancreatic head. The patient underwent a pylorus-preserving pancreaticoduodenectomy, and pathology was positive for cells staining for pancreatic polypeptide, insulin, and occasional double hormone (insulin plus pancreatic polypeptide)-positive cells. In addition, the tumor exhibited broad staining for ALDH1A3, a new marker of endocrine progenitors. This case serves to highlight the clinical and pathologic variability of insulin-producing tumors and raises the potential for cells in these tumors to exhibit hormone interconversion and progenitor-like states.
Keywords: hypoglycemia; insulin; neuroendocrine tumor; pancreatic polypeptide.