Which analysis of pancreatic cyst fluid is the most accurate tumor marker for diagnosing mucinous cysts?

• A. Amylase
• B. Glucose
• C. CEA
• D. Mucin

Answer: (C)

Pancreatic cyst fluid analysis aims to separate mucinous from nonmucinous cysts. Mucinous cysts arise from mucin-producing epithelium, so a marker that reflects this mucinous biology is most informative. Carcinoembryonic antigen (CEA) in the cyst fluid is the best-studied discriminator for this purpose: high CEA levels consistently point to a mucinous cyst, while nonmucinous cysts tend to have low CEA. A commonly used cutoff around 192 ng/mL helps differentiate them with useful sensitivity and specificity. Amylase, by contrast, highlights ductal communication and is more associated with pseudocysts; glucose can be lower in mucinous cysts but is less specific. Mucin itself isn’t as reliable as a diagnostic marker in routine practice. So, CEA in cyst fluid best identifies mucinous pancreatic cysts.