EUS-FNA is the standard of care for diagnosing pancreatic masses. According to the operator's preference, EUS-FNA with suction or without suction technique has been used. To date, little is known about optimal number of to-and-fro motion during each needle pass. As usual 10-15 to-and-fro motions was used for EUS-FNA with suction technique. Theoretically, more number of to-and-fro motions may be required in EUS-FNA without suction. In this circumstance, the contamination of blood in specimen and possible adverse event may occur. To determine optimal number of to-and-fro motion in EUS-guided FNA for pancreatic masses in terms of with suction or without suction, this prospective single-blinded randomized trial was conducted.

For this prospective single-blinded randomized trial, two 10cc syringes was prepared. Two syringe was provided as same performance. However, one syringe is falsely made as suction syringe (fake one). During EUS-FNA, two syringe is randomly assigned and loaded by a nurse. Thus, operator was blinded which syringe is with suction or without suction.

First hypothesis: There is difference in the diagnostic accuracy of pancreatic masses according to EUS-FNA with suction or without suction/ different number of to-and-fro motion.

Second hypothesis: There is difference in the amount of blood in samples obtained by EUS-FNA with suction or without suction/ different number of to-and-fro motion.

Inclusion Criteria:

• Age > 19 years Solid pancreatic mass lesions

Exclusion Criteria:

• Age < 19 years Coagulopathy Unable to consent