When to puncture, when not to puncture: Submucosal tumors.

Subepithelial masses of the gastrointestinal (GI) tract are a frequent source of referral for endosonographic evaluation. Subepithelial tumors most often appear as protuberances in the GI tract with normal overlying mucosa. When there is a need to obtain a sample of the mass for diagnosis, endoscopic ultrasound (EUS) - guided fine-needle aspiration (FNA) is superior to other studies and should be the first choice to investigate any subepithelial lesion. When the decision is made to perform EUS-guided FNA several technical factors must be considered. The type and size of the needle chosen can affect diagnostic accuracy, adequacy of sample size and number of passes needed. The use of a stylet or suction and a fanning or standard technique during EUS-guided FNA are other factors that must be considered. Another method proposed to improve the efficacy of EUS-guided FNA is having an on-site cytopathologist or cytotechnician. Large or well-differentiated tumors may be more difficult to diagnose by standard EUS-FNA and the use of a biopsy needle can be used to acquire a histopathology sample. This can allow preservation of tissue architecture and cellularity of the lesion and may lead to a more definitive diagnosis. Alternatives to FNA such as taking bite-on-bite samples and endoscopic submucosal resection (ESMR) have been studied. Comparison of these two techniques found that ESMR has a significantly higher diagnostic yield. Most complications associated with EUS-FNA such as perforation, infection and pancreatitis are rare and the severity and incidence of these adverse events is not known. Controversy exists as to the optimal method in which to perform EUS-FNA and larger prospective trials are needed.