What is the cyst marker profile for a pancreatic pseudocyst?

• A. No mutation, high amylase, low CEA
• B. KRAS mutation, low amylase, high CEA
• C. GNAS mutation, high amylase, low CEA
• D. CTNNB1 mutation, low amylase, high CEA

Answer: (A)

Cyst fluid analysis helps differentiate pancreatic pseudocysts from mucinous cystic neoplasms by looking at enzyme content, tumor markers, and genetic mutations. A pseudocyst usually communicates with the pancreatic ducts, so its fluid is rich in pancreatic enzymes (high amylase) but does not have mucinous features, reflected by a low CEA and no oncogenic mutations detected. That combination—high amylase, low CEA, and no detectable mutations—best fits a pancreatic pseudocyst profile.

If the fluid showed a mutation such as KRAS or GNAS, or had a high CEA level, that would suggest a mucinous cystic neoplasm or IPMN rather than a pseudocyst, because those lesions tend to harbor mucinous biology and elevated tumor markers.