Yield of Endoscopic Ultrasound Guided Fine Needle Aspiration (EUS-FNA) With and Without the Use of a Stylet in the Biopsy Needle

Purpose: To compare the diagnostic yield of endoscopic ultrasound guided fine needle aspiration biopsy (EUS-FNA) in patient with pancreatic masses with and without the use of a stylet in place within the biopsy needle. Hypothesis: In patients undergoing an EUS FNA for pancreatic indications, patients having a fine needle aspiration biopsy (FNA) without the internal stylet will have a greater diagnostic yield compared to those with the internal stylet. Justification: EUS-FNA is an increasingly important means of obtaining tissue samples from lesions within the thorax and abdomen. In experienced hands EUS-FNA is a safe alternative to more invasive procedures such as mediastinoscopy or laparoscopy. EUS-FNA can be used for sampling suspected cholangiocarcinoma, pancreatic masses or cysts, submucosal gastric lesions, peripancreatic, perigastric or mediastinal lymph nodes and in some cases adrenal or liver masses. Therefore, it is a powerful tool for both diagnosis and tumour staging. For example, for the diagnosis of pancreatic adenocarcinoma, which is a common indication for EUS-FNA, the sensitivity varies from 75 to \>90%, with a specificity of 82-100% and a mean accuracy of 85%. Improving the diagnostic yield may lead to an earlier diagnosis with a reduced number of investigations and earlier institution of treatment for the patient. The FNA needle system consists of a 22 or 19 gauge needle which is manipulated by a handle piston that attaches to the biopsy channel of the endoscopic ultrasound (EUS) linear scope. The tip of the needle has grooves to disperse ultrasound waves making the tip of the needle easily seen. The sample is taken by inserting a specially designed needle into the area of interest under EUS guidance. Inside the needle is a removable stylet with a rounded or bevelled tip to facilitate the passage of the needle into the tissue. The usual practice is for the stylet to be extracted after the needle has been passed into its optimum position withi