['Differential diagnosis of pancreatic cystic lesions may be difficult: the main problem is to distinguish mucinous neoplasms from nonmucinous cysts. We evaluated the usefulness of the mucin-like carcinoma-associated antigen (MCA) in the fluid of pancreatic cysts for detecting mucinous neoplasms. Results were compared with those of CA 15-3, carcinoembryonic antigen (CEA), and CA 72-4 fluid content, and cytology.', 'Twenty-four pancreatic cyst fluids were collected from 10 pseudocysts, eight mucinous cystic tumors, and six serous cystadenomas.', 'MCA was elevated in seven of eight mucinous tumors (sensitivity 87.5%, specificity 100%). A significant difference was found between MCA levels in mucinous neoplasms versus pseudocysts (p = 0.0003) and serous cystadenomas (p = 0.001). Mean MCA levels were higher (133.7 U/ml) in mucinous cystadenocarcinomas than in cystadenomas (37.5 U/ml). The sensitivity of CA 15-3, CEA, and CA 72-4 in detecting mucinous neoplasms was 50, 87.5, and 87.5%, respectively, with a specificity of 94%, 44%, and 94%, respectively. Cytology showed mucinous epithelial cells in only four of eight mucinous neoplasms, with a specificity of 100%.'] Does expression of mucin-like carcinoma-associated antigen in the cyst fluid differentiate mucinous from nonmucinous pancreatic cysts?