Cytology adds value to monoclonal antibody Das-1 testing for detection of high-risk pancreatic cysts

Introduction: Determining the risk of malignancy in a pancreatic cyst (PC) is a clinical and diagnostic challenge. Monoclonal antibody (mAb) Das-1 test was shown to have high sensitivity, specificity, and accuracy in detecting high-risk (HR) cysts. Das-1 mAb test detects HR mucinous cysts with high-grade dysplasia (HGD), invasive carcinoma, and/or intestinal-type epithelium. Correlation of mAb Das-1 testing of PC fluids with cytomorphologic findings has not been evaluated. Materials and methods: We correlated cytology with mAb Das-1 test results and resection histology in 26 PCs. There were 18 intraductal papillary mucinous neoplasms (IPMN), 1 intraductal oncocytic papillary neoplasm (IOPN), 4 mucinous cystic neoplasms (MCN), 2 serous cystadenomas, and 1 cystic pancreatic neuroendocrine tumor (PanNET). HR cysts included cysts with high-grade atypia on cytology or HGD on histology, invasive carcinoma, IOPNs, and cystic PanNETs. Intestinal type IPMNs were also HR cysts on histology. Results: In 17 cases (65.38%), cytology and mAb Das-1 test correlated with histology. There were 2 (7.69%) mAb Das-1 test negative HR PCs diagnosed by cytology. Five (19.23%) mAb Das-1 test positive HR PCs had mucin only or cells with low-grade dysplasia on cytology. Two mAb Das-1 test positive HR PCs had nondiagnostic cytology. HR IOPN and cystic PanNET were not detected by mAb Das-1 test. Conclusion: The mAb Das-1 is a sensitive and specific biomarker for detecting HR mucinous PCs. Adding cytology to mAb Das-1 testing improves the sensitivity for the detection of nonmucinous HR PC. Together, cytology with mAb Das-1 testing is more accurate than either one alone.