What is the cyst marker profile for a cystic pancreatic neuroendocrine tumor (pNET)?

• A. KRAS mutation, high amylase, high CEA
• B. GNAS mutation, high amylase, low CEA
• C. CTNNB1 mutation, high amylase, low CEA
• D. MEN1/TSC2 mutation, low amylase, low CEA

Answer: (D)

Pancreatic cystic neuroendocrine tumors have a biochemical and genetic profile that sets them apart from other pancreatic cysts. In cyst fluid, amylase and CEA are typically low, indicating non-ductal content and a lack of mucinous material. Genetically, these tumors are associated with alterations in MEN1 and, less commonly, TSC2. This combination—low cyst fluid amylase, low CEA, and MEN1/TSC2 mutations—best fits a cystic pNET.

Other cystic lesions often show different patterns: pseudocysts tend to have high amylase due to pancreatic enzyme leakage; mucinous cysts (like IPMN or MCN) usually have high CEA and distinct mutations such as GNAS or KRAS; none of those align with the MEN1/TSC2, low amylase, low CEA profile.