Background & aims: Current methods to detect malignancy in mucinous cystic neoplasms of the pancreas remain inadequate. The role of detailed molecular analysis in this context was investigated.
Methods: Endoscopic ultrasound-guided pancreatic cyst aspirates were prospectively collected during a period of 19 months and studied for cytology, carcinoembryonic antigen level, and molecular analysis. Molecular evaluation incorporated DNA quantification (amount and quality), k-ras point mutation, and broad panel tumor suppressor linked microsatellite marker allelic loss analysis by using fluorescent capillary electrophoresis. The sequence of mutation acquisition was also calculated on the basis of a clonal expansion model, and comparison was made to the final pathology.
Results: Thirty-six cysts with confirmed histology were analyzed. There were 11 malignant, 15 premalignant, and 10 benign cysts. Malignant cysts could be differentiated from premalignant cysts on the basis of fluid carcinoembryonic antigen level (P=.034), DNA quality (P=.009), number of mutations (P=.002), and on the sequence of mutations acquired (P<.001). Early k-ras mutation followed by allelic loss was the most predictive of a malignant cyst (sensitivity, 91%; specificity, 93%).
Conclusions: Malignant cyst fluid contains adequate DNA to allow mutational analysis. A first hit k-ras mutation followed by allelic loss is most predictive of the presence of malignancy in a pancreatic cyst. This approach should serve as an ancillary tool to the conventional work-up of pancreatic cysts. Cumulative amount and timing of detectable mutational damage can assist in diagnosis and clinical management.