Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) is an important investigation tool to obtain tissue for diagnosis. Nowadays, the performance of EUS-FNA varies with accuracy rates ranging from 60% - 100%. Needles with different diameters have been explored to retrieve tissue specimens. The diagnostic yields, successful rates and safety profiles are similar. It has been suggested that although thinner needles provide less cellular material than do larger needles, the specimens from the former are less contaminated by blood, and thus easier to interpret. In addition, thinner needles may be easier to use because of greater flexibility, particularly for locations requiring important scope bending. As a result, a new 22G FNA needle has been designed in order to improve the tissue-sampling rate (ECHO-HD-22-C, Cook Endoscopy, USA). There is a reverse bevel at the tip of the new needle with promotes collection of core sample by shearing material from target lesion during retrograde movement of the needle in the lesion. The feasibility and safety of this newly design EUS-FNA needle have been demonstrated in a recent multicenter, pooled, cohort study using the 19G version. Successful puncture was technically feasible in 98.2% of cases and the overall accuracy of 92.9%. There were no complications related to the technique.

The aim of this study is to compare the tissue-sampling rate and the diagnostic accuracy rate of EUS-FNA between the uses of the convention and newly designed 22-gauge needles.

Endoscopic ultrasound (EUS) - guided fine needle aspiration (FNA) is a well-established technique for tissue sampling of intestinal and extra-intestinal mass lesions. The accuracy of EUS-guided FNA varies from 60% - 100% with a complication rate of 0% - 3%. The diagnostic accuracy of the procedure can be improved by the use immunohistochemical studies and genetic analyses.It may also be improved by obtaining a larger biopsy specimen with a core biopsy needle. However, puncturing with a core-biopsy needle may not be always feasible due to the technical difficulty of inserting the larger needle through the bended endoscope. As a result, the advantage of a core-biopsy needle on providing a larger amount of cellular material is offset by a higher rate of technical failures, especially in the setting of a transduodenal puncture. Recently, a new 22G FNA needle with a reverse bevel at the tip has become available (ECHO-HD-22-C, Cook Endoscopy, USA.). The design of the device promotes the collection of core samples by shearing material from target lesion during retrograde movement of the needle in the lesion. Hence, the aim of this study is to compare the tissue-sampling rate and the diagnostic accuracy rate of EUS-FNA using 22G conventional and Procore needles.

Inclusion Criteria:

• Ages of 18-80 undergoing EUS-guided tissue acquisition
• Informed consent available

Exclusion Criteria:

• Coagulopathy
• Previous history of upper gastrointestinal surgery
• Contraindications for conscious sedation
• Pregnancy