Mucin Stain of Endoscopic Ultrasound-Guided Pancreatic Cyst Fluid Is Independently Predictive of Mucinous Cystic Neoplasms

Abstract

Aim: The optimal management of pancreatic cystic neoplasms is not well established. Endoscopic ultrasound (EUS) has now enabled us to safely aspirate cystic lesions for cyst fluid analysis. Thick fluid consistency can limit the volume of aspirate and thereby affect the type of test performed. Mucin staining of the fluid is simple and does not require a significant volume to perform. The aim of our study was to correlate positive mucin stain with surgical pathology. Method: This is a retrospective chart review of all patients who underwent EUS for pancreatic cysts between Feb 2004 and Aug 2006 at the University of Alberta Hospital, Edmonton, Alberta. Cyst fluid was analyzed for malignant cytology, mucin stain and amylase. Patients underwent surgery or were followed conservatively as determined by the result of mucin staining and operability as determined by the surgeon. Result: EUS was performed on 48 patients with pancreatic cystic lesions. There were 29 females. The mean age was 61 yrs (range 28-84 yrs). A total of 43 patients underwent EUS-guided FNA. Results of mucin staining were available for 37 patients. Of these, 26 patients had a positive mucin stain (70%). 15/26 patients with positive mucin stain underwent surgery. Of these, 14 patients were found to have a neoplastic lesion (mucinous cystadenoma in 5, mucinous cystadenocarcinoma in 3, IPMT in 5 and oncocytic neoplasm in 1). Only 1/15 patients had a benign serous cystadenoma. The correlation between positive cyst fluid mucin staining and mucinous cystic neoplasms on histology is 93%. Of the 11 patients with negative mucin staining, 1 patient underwent surgery for persistent abdominal pain and was found to have a serous cystadenoma. Seven patients were followed conservatively for at least 6 months. Three patients were lost to follow-up. Conclusion: Mucin staining of pancreatic cyst fluid appears to be highly predictive of mucinous cystic neoplasms. Further diagnostic testing may not be indicated as most patients are offered surgery. Mucin negative pancreatic cysts, however, represent a management dilemma. As a subset of these patients may have a mucinous neoplasm, further testing with CEA may help clarify those that should undergo surgery. Further prospective studies are needed to confirm this.