What are the subtypes and syndromes of functional PNETS?
Insulinoma is the most common functional PNET and is malignant in < 10% of cases. The most common presenting symptom is hypoglycemia, causing neuroglycopenic or cardiovascular symptoms. These tumors are found in an even distribution through the entire pancreas.
Gastrinoma is the second most common functional PNET and causes Zollinger-Ellison syndrome (ZES). Approximately 60% to 90% are malignant. The most common presenting symptoms are severe peptic ulcer disease, abdominal pain, and diarrhea. The vast majority (70%–95%) of gastrinomas are located in the first portion of the duodenum and not in the pancreas, as previous studies had suggested.
Glucagonoma is the next most common functional PNET and 50% to 80% of these tumors are malignant. The most common presenting symptoms are necrolytic migratory erythema, diabetes, deep vein thrombosis, and diarrhea. These tumors are found in an even distribution through the entire pancreas, are often quite large, and usually present with metastases.
VIP–secreting tumors (VIPomas) are rare, malignant 40% to 70% of the time, and present with watery diarrhea, hypokalemia, and achlorhydria (also known as Werner-Morrison syndrome ). The most common tumor locations are the body and tail of the pancreas.
Somatostatinomas are the rarest functional PNETs and are malignant > 70% of the time. The most common presenting symptoms are diabetes, steatorrhea, and cholelithiasis. These tumors are most commonly found in the pancreas (55%) or the proximal small bowel (duodenum/jejunum; 44%).