The goal of this clinical trial is to learn about the feasibility of collecting pancreatic juice through duodenal aspiration by ultrasound endoscopy (EUS) for molecular marker testing after intraduodenal infusion of vinegar in patients with suspected pancreatic cancer and who are scheduled to have endoscopic ultrasound with fine needle aspiration (EUS-FNA). The main questions it aims to answer are:

• Is vinegar-induced collection of duodenal pancreatic juice via endoscopic ultrasound feasible?
• What is the best operating condition (amount of vinegar, collection time, etc.) of vinegar-induced collection of duodenal pancreatic juice via endoscopic ultrasound?

Participants will have EUS as scheduled, during which different amount of vinegar will be infused into duodenum and then pancreatic juice be collected for different time via suction by EUS.

Researchers will compare the amount of collected pancreatic juice and molecular marker level in different groups to determine the best operating condition for vinegar-induced collection of duodenal pancreatic juice via endoscopic ultrasound.

This is a single center, prospective, randomized-controlled study. Participants who are diagnosed as suspected pancreatic cancer and are schedule to have EUS-FNA will have saline or different amount of vinegar infused into duodenum and pancreatic juiced collected via EUS suction during different period of time under intravenous anesthesia.

The collected pancreatic juice will be weighed instantly and frozen in 10 minutes under -80℃ for further tests.

Researchers will compare the weight, cfDNA (cell free DNA) concentration, PLA2G1B (Phosphatidylcholine 2-acylhydrolase 1B) concentration, immunoglobulin concentration and KRAS (Kirsten rat sarcoma viral oncogene) mutation load of collected pancreatic juice from different arms.

Inclusion Criteria:

• Age: 18 years old or older
• Diagnosis: CT, MRI, transabdominal ultrasound or other imaging examinations showed a pancreatic mass, and 3 endoscopists agreed on the diagnosis of suspected pancreatic cancer
• EUS-FNA is required to perform further treatment strategy
• The patient can understand the study protocol, is willing to participate in the study and can provide written informed consent

Exclusion Criteria:

• The patient's clinical and imaging features do not support the diagnosis of suspected pancreatic cancer, judged by 3 endoscopists
• The patient refuses to have EUS-FNA
• The patient is unsuitable for EUS-FNA because of his/her general condition, or contraindicated for anesthesia
• The patient's imaging suggests severe pancreatic duct obstruction
• The patient cannot understand the conditions and objectives of this study, or refuse to participate in the study