Prospective analysis of atypical epithelial cells as a high-risk cytologic feature for malignancy in pancreatic cysts

BACKGROUND: Pancreatic cysts are aspirated to assess whether a cyst is mucinous on one hand and malignant on the other. The authors' retrospective data have indicated that high-grade atypical epithelial cells (AECs) identified on cytology are a high-risk feature and a better threshold than "positive" for detecting malignancy. The objective of the current study was to assess the accuracy of AECs in predicting malignancy in pancreatic cysts. METHODS: Cysts aspirated by endoscopic ultrasound (EUS)-guided fine-needle aspiration (EUS-FNAs) obtained between January 2006 and June 2011 were evaluated. Cytologic, histologic, imaging, and cyst fluid analysis data were recorded. AECs were defined as cells that had an increased nuclear-to-cytoplasmic ratio and nuclear hyperchromasia with or without membrane abnormalities and with or without cytoplasmic vacuoles, but of insufficient quality and quantity for a "positive" interpretation. Malignancy included mucinous cysts with high-grade dysplasia and invasive carcinoma. Performance characteristics of cytology with AECs or worse (high-grade atypia [HGA]) for predicting malignancy were assessed. RESULTS: There were 70 FNAs that had histologic confirmation from 404 EUS-FNAs in 352 patients. Excluding 4 nondiagnostic FNAs, the study cohort consisted of 66 FNAs for analysis. There were 24 malignant cysts with 20 true-positive, 4 false-negative, 36 true-negative, and 6 false-positive results. For the detection of malignancy, HGA had 83% sensitivity, 86% specificity, a positive predictive value of 77%, a negative predictive value of 90%, and 85% overall accuracy. The lower threshold for malignancy with AECs resulted in a 12% increase in the detection of malignancy. CONCLUSIONS: A finding of AECs on cytology is a highrisk feature for malignancy and is an accurate triage threshold for resection.