Pancreatic endocrine tumors

PanNETs - The Hormone Factory

• Rare neuroendocrine tumors originating from islet cells; can be functional (hormone-secreting) or non-functional (mass effects).
• Well-differentiated, uniform cells arranged in nests or trabeculae.
• Histology classic: "salt-and-pepper" chromatin.
• Immunohistochemistry markers: Synaptophysin and Chromogranin A are key for diagnosis.

⭐ PanNETs are strongly associated with Multiple Endocrine Neoplasia Type 1 (MEN1), particularly gastrinomas and insulinomas.

Insulinoma - Sugar Sponge Scramble

• Most common functional pancreatic endocrine tumor; typically benign (~90%).
• Tumor of pancreatic β-cells → ↑↑ Insulin secretion, acting like a "sugar sponge".
• 📌 Whipple's Triad for diagnosis:
  • Symptoms of hypoglycemia (e.g., confusion, seizures, diaphoresis).
  • Low plasma glucose measured at the time of symptoms.
  • Relief of symptoms after glucose administration.

⭐ Elevated C-peptide is crucial; it differentiates endogenous insulin production from exogenous insulin administration (where C-peptide would be low).

• Often associated with MEN1 syndrome.

Gastrinoma - Acid Overdrive Ulcers

• Definition: Gastrin-secreting neuroendocrine tumor (NET), most commonly found in the duodenum or pancreas.
• Syndrome: Causes Zollinger-Ellison Syndrome (ZES) due to massive gastrin production.
• Pathophysiology: ↑ Gastrin → Parietal cell hyperplasia → ↑ HCl secretion.
• Clinical Picture:
  • Multiple, treatment-refractory peptic ulcers, often in unusual locations (e.g., jejunum).
  • Chronic diarrhea & steatorrhea (acid inactivates pancreatic lipase).
  • Abdominal pain, heartburn.
• Diagnosis:
  • ↑ Fasting serum gastrin (>100 pg/mL).
  • Secretin stimulation test confirms.

⭐ Exam Favorite: The secretin stimulation test is key. Normally, secretin inhibits gastrin release. In gastrinoma, it paradoxically stimulates it, causing a sharp rise in serum gastrin.

Rare Tumors - Alphabet Soup Syndromes

• Somatostatinoma: Presents with a triad of mild diabetes, cholelithiasis (due to ↓ CCK), and steatorrhea. Often malignant.
• VIPoma (WDHA Syndrome): Causes profuse Watery Diarrhea, Hypokalemia, and Achlorhydria. Associated with MEN1.
• Glucagonoma: Characterized by the 4 D's: Dermatitis (necrolytic migratory erythema), Diabetes (often mild), DVT, and Depression.

⭐ Necrolytic migratory erythema is a key finding for Glucagonoma, presenting as a painful, pruritic rash typically on the face, perineum, and extremities.

High‑Yield Points - ⚡ Biggest Takeaways

• Insulinomas are the most common, causing hypoglycemia and diagnosed by the Whipple triad.
• Gastrinomas (Zollinger-Ellison syndrome) lead to refractory peptic ulcers and are strongly associated with MEN1.
• Glucagonomas are characterized by necrolytic migratory erythema, diabetes, and weight loss.
• VIPomas cause WDHA syndrome (Watery Diarrhea, Hypokalemia, Achlorhydria).
• Somatostatinomas present with a classic triad: diabetes mellitus, cholelithiasis, and steatorrhea.
• Most are well-differentiated neuroendocrine tumors (NETs).