EUS-guided Fine Needle Aspiration (FNA) With and Without the Use of a Stylet

Endoscopic ultrasound (EUS)-guided fine needle aspiration (FNA) is a highly accurate method for cytologic diagnosis of malignancy and is routinely performed to diagnose and stage pancreatobiliary, esophageal, gastric, rectal malignancies and subepithelial gastrointestinal lesions. There are variations in EUS-FNA technique including the use of suction, the area of the lesion to target (center versus periphery), gauge of needle, and use of a stylet.

The stylet is a metal wire which is included in the needle assembly. The use of a stylet is used purely for mechanical purposes, not for the protection or safety of the patients. It is thought that the stylet prevents the needle from becoming clogged with gastrointestinal epithelial cells or mucus. To our knowledge, comparing the diagnostic accuracy of EUS-FNA with a stylet to the accuracy without a stylet has not been studied.

The optimal technique for EUS-FNA has not been established. The reported accuracy rate of EUS-FNA (which contains heterogeneous sampling techniques, including with and without a stylet) is 71-98% for pancreatic masses, 90% for lymph nodes, and 67-92% for submucosal gastrointestinal lesions. Typically, FNA is performed with or without a stylet using a 22 gauge or 25 gauge needle with similar diagnostic accuracy.

When the target lesion is identified, the needle is advanced through the gastrointestinal wall into the lesion under ultrasound guidance. If a stylet is being used, it is removed at this point. A 10 cc syringe under suction is then placed on the end of the needle assembly and the needle is moved back and forth within the lesion to gather cells. The assembly is then removed and the needle contents are expelled onto slides and into preservative media. The stylet is then reinserted and the needle assembly is advanced through the scope for another pass. In the absence of on-site cytopathology, 7 passes with or without a stylet of a solid lesion and 5 passes of lymph nodes with or without a stylet are recommended to achieve high diagnostic accuracy.

EUS-FNA is time consuming, mainly because the stylet needs to be carefully reinserted through the needle prior to each pass. Theoretically, the use of a stylet prevents clogging of the needle with gastrointestinal epithelial cells and mucus which can affect the adequacy of the specimen. However, there are no data to support this. As such there is a variation in practice patterns, with some endosonographers who routinely use a stylet and those that do not. Additionally, those who perform percutaneous FNA frequently do so using needles that do not have a stylet. A recent study suggests that the use of a stylet improves diagnostic accuracy in percutaneous FNA of thyroid lesions. To our knowledge, there have been no studies assessing the use of a stylet on tissue adequacy in EUS-guided FNA.

If the practice of using a stylet during EUS-guided FNA is found to yield the same number of adequate tissue samples as those done without a stylet, then the use of a stylet would be an unnecessary. As stylet replacement is the most time consuming step in FNA, the time of the procedure could be shortened significantly if the stylet is not required.

We propose a randomized controlled trial of EUS guided FNA with and without stylet which will help determine whether the use of a stylet is integral in obtaining adequate tissue aspirates in the diagnosis of solid lesions. To our knowledge, there have been no prospective, randomized studies addressing the effect of the presence or absence of a stylet on specimen adequacy during EUS-guided FNA.

Inclusion criteria

• patients referred to the Washington University Interventional Endoscopy Division for EUS-guided FNA of a solid lesion (e.g. pancreatic mass, gastric wall mass, or lymphadenopathy)

Exclusion criteria

• Patients <18 years of age
• patients who cannot provide independent informed consent (i.e. patients with dementia or with a health care proxy)
• pregnant women (as determined by pregnancy test given as part of standard of care)
• prisoners