Cytology may provide valuable information and is diagnostic in many cases, but it is limited by sampling difficulties. Performance of mucin stains and analysis of the cyst fluid for tumor markers, as described in the article on histology of cystic neoplasms elsewhere in this issue, increase detection of MCNs and IPMNs; however, as with any other laboratory test, the results of the cyst fluid cytologic analysis need to be assessed in light of the clinical and radiologic findings, particularly when the cytology is not completely diagnostic.