Pancreatic Cysts Fluid Analysis: CEA, Cytology, and K-Ras

Abstract

Purpose: Accurate diagnosis of a pancreatic cyst is often difficult. A number of methods have been employed utilizing EUS/FNA, including analysis of cyst fluid for CEA, cytology, and more recently K-Ras gene mutation. K-Ras mutation has been shown to be the most specific of these, but not very sensitive. Often, a cyst aspirate can only be sent for one or two of these three markers due to limited amount of fluid within the cyst. The purpose of this study is to identify the combination of markers which would provide the best chance for the correct diagnosis. Methods: After obtaining IRB approval, we obtained the medical record numbers of all patients seen at UMMHC from October 2003 through December 2011 who were coded with ICD-9 code 577.2, which represents the diagnosis of pancreatic cyst or pseudocyst. Of these, we included in our study those cases that had K-Ras analysis and/or came to a definitive diagnosis (surgical pathology). We then compared the utility of different cyst fluid markers (and their combinations) in making the correct pathological diagnosis. Results: We identified 111 unique cases, and 61 cases which were repeat EUS/FNA procedures, for a total of 172 cases. The Table below summarizes the results. Our results revealed that the combination of K-Ras gene analysis and cytology has the best sensitivity and accuracy, and is tied for the best specificity, positive predictive value, and negative predictive value.Table: No Caption available.Conclusion: Our results suggest that analyzing the cyst fluid for the K-Ras mutation and cytology gives the best chance of making the correct diagnosis. One of the problems with cytology is that the aspirate is often non-diagnostic due to the acellular nature of the cyst. Before abandoning CEA testing, a larger study needs to be performed to confirm these results. Additionally, improving cytology yields can further enhance the utility of combining these two markers.