A 42-year-old woman has three months of episodic confusion, sweating, and palpitations relieved by eating. During a monitored fast she develops symptomatic hypoglycemia with plasma glucose of 38 mg/dL, insulin level of 18 microU/mL, and negative sulfonylurea screen. Imaging localizes a 1.2 cm pancreatic body lesion. The most likely diagnosis is:

• A Gastrinoma
• B Insulinoma ✓
• C Glucagonoma
• D Serous cystadenoma

Explanation

The combination of neuroglycopenic symptoms, glucose below 55 mg/dL, and inappropriately elevated insulin during a supervised fast constitutes Whipple triad, the hallmark of insulinoma. Insulinoma is the most common functioning pancreatic neuroendocrine tumor, usually solitary, small, and curable by enucleation, with roughly 10 percent associated with MEN1. Gastrinoma causes Zollinger-Ellison syndrome with peptic ulcers, glucagonoma causes necrolytic migratory erythema and diabetes, and serous cystadenoma is nonfunctional.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.