Determination of tumor marker levels in cystic fluid of benign liver cysts

The levels of tumor markers in cystic fluid and serum were measured in six patients with benign biliary cyst of the liver. AFP in the cystic fluid was lower than the upper normal limit for serum in all cases, and CEA in the cystic fluid was higher than the upper normal limit for serum in one of the six cases. CA19-9, DU-PAN 2, and SPAN 1 in cystic fluid were much higher than the upper normal limit for serum in all cases (more than 100-fold for CA19-9, twofold for DU-PAN 2, and ninefold for SPAN 1). CA19-9, DU-PAN 2, and SPAN 1 in cystic fluid were significantly higher than the levels in the corresponding serum. Positive immunohistochemical staining against CA19-9, DU-PAN 2, and SPAN 1 was observed in the cytoplasm of the epithelial cells of the cyst wall. These results suggested that the high concentrations of CA19-9, DU-PAN 2, and SPAN 1 in the cystic fluid were due to secretion from the epithelial cells in the benign biliary cysts.