Cyst fluid analysis in the differential diagnosis of pancreatic cysts: a new approach to the preoperative assessment of pancreatic cystic lesions.

Pancreatic cysts include pseudocysts, serous tumors, and mucinous tumors, some of which are malignant. The clinical and radiologic features of these lesions may not permit a preoperative diagnosis. Analysis of percutaneous cyst fluid aspirates for cytologic findings, tumor markers, enzymes, and viscosity has been proposed as an aid to differential diagnosis. The combination of cytologic findings, carcinoembryonic antigen level, and viscosity will usually differentiate mucinous from nonmucinous cysts, whereas cytologic findings and levels of tumor markers CA 15-3 and CA 72-4 are useful to predict malignancy. Pseudocysts can be identified by a combination of cytologic features; levels of tumor markers, including NB/70K; and levels of enzymes, including amylase isoenzymes and leukocyte esterase. Serous tumors are a diagnosis of exclusion, although in 50% of cases the cytologic findings will indicate a serous tumor. When compared with conventional methods of differentiating pancreatic cysts, cyst fluid analysis is a promising new approach to the evaluation of these diagnostically difficult lesions.