Giant 12 cm Pancreatic Insulinoma: Tumor Evolution, Management, and Pathologic Considerations

ABSTRACT Insulinomas are characteristically small pancreatic neuroendocrine tumors, though giant variants have been reported. We describe a 63-year-old woman who presented with refractory hypoglycemia attributable to an exceptionally large 12 cm pancreatic mass that failed to respond to medical treatment. She was quickly taken for surgical resection, after which hypoglycemia quickly resolved. Histopathologic examination demonstrated a well-differentiated pT3N0 neuroendocrine tumor demonstrating negative staining for insulin and pancreatic and duodenal homeobox 1, with positive staining for insulinoma-associated protein 1, alpha-thalassemia/mental retardation X-linked, and alpha-1-antitrypsin. Repeat imaging showed no tumor recurrence. This case illustrates an uncommon presentation and highlights key immunostains in delineating different insulinoma phenotypes.