Clinical assessment compared with cyst fluid analysis in the differential diagnosis of cystic lesions in the pancreas

Background. In adults 80% to 90% of cystic lesions in the pancreas are pseudocysts and the remainder are mostly neoplastic cysts. To choose optimal treatment for an individual patient, exact nonoperative diagnosis would be preferable. This study was done to assess the value of cyst fluid analysis, compared with clinical and radiologic findings, in the differential diagnosis of pancreatic cystic lesions. Methods. Twenty-two patients with a cystic lesion in the pancreas underwent operation, cyst wall biopsy, and aspiration of cyst fluid. Carcinoembryonic antigen (CEA), CA 19-9, pancreatitis-associated protein (PAP), and total protein concentration, amylase activity, and cytologic findings were studied. Final diagnosis was pseudocyst in 14 patients, serous cystadenoma in two, mucinous cystadenoma in two, and mucinous cystadenocarcinoma in four patients. Results. Clinical and radiologic judgment correctly differentiated pseudocysts and neoplastic cysts. Cyst fluid aspiration did not succeed in two patients with mucinous cystadenocarcinomas because of the high fluid viscosity. Cyst fluid amylase activity was high (greater than 16,000 IU/ml) in all but one pseudocyst and low (less than 83 IU/ml) in all but one neoplastic cyst. CEA level was lower in pseudocysts than in neoplastic cysts, but with an overlapping value between the groups. Mean CA 19-9 concentration was higher in pseudocysts than in neoplastic cysts, but with wide overlap between the groups. Pancreatitis-associated protein and total protein concentration and cystic fluid cytologic findings did not differ between various types of cysts. Conclusions. Clinical judgment including careful history and radiologic studies seems to be the most reliable method of differentiating neoplastic pancreatic cysts from pseudocysts. Amylase and CEA levels give suggestive information, but cyst fluid analysis may be misleading in an individual patient.