A 45-year-old woman has three years of episodic sweating, tremor, palpitations, and confusion relieved promptly by eating. Supervised fasting shows plasma glucose of 42 mg/dL with inappropriately elevated insulin and C-peptide, and a negative sulfonylurea screen. Imaging localizes a 1.2 cm pancreatic tail lesion. The most common functional pancreatic neuroendocrine tumor is:
- A Insulinoma ✓
- B Glucagonoma
- C Gastrinoma
- D VIPoma
Correct answer: A. Insulinoma
Explanation
Insulinoma is the most frequent functioning pancreatic neuroendocrine tumor and typically presents with Whipple's triad: neuroglycopenic symptoms during fasting, biochemically documented hypoglycemia below 55 mg/dL, and prompt relief with glucose administration. Elevated A-peptide with a negative sulfonylurea screen excludes exogenous insulin or drug-induced hypoglycemia. Most insulinomas are small, solitary, and behave indolently, unlike gastrinomas which are frequently malignant.
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.