EUS-guided tissue acquisition is an established modality to diagnose malignancies of the pancreas and extrahepatic bile ducts. In the recent years fine needle biopsy (FNB) needles have largely replaced fine needle aspiration (FNA) for EUS-guided tissue acquisition. The Acquire FNB needle is a Franseen needle which has three symmetric cutting edges to obtain core tissue specimens. The Trident FNB needle has been recently introduced to the market for EUS-guided tissue acquisition. It has a multi-blade three-prong tip which one of the tips is longer than the other two.

The aim of this study is to prospectively compare these two types of needle in term of diagnostic accuracy, and safety profile.

Patients with solid mass lesions in the pancreas or extrahepatic biliary system will be randomly assigned to one of two types of FNB needle. Four passes of FNB will be acquired from the mass lesion in each patient. The primary aim is to compare sensitivity of two types of FNB needle to diagnose malignancy. Also, each pass of FNB needle will be assessed separately by two expert pathologists to determine per-pass sensitivity of two types of FNB needles.

Inclusion Criteria:

• Inpatients and outpatients 18 years of age or older with solid mass lesions in the pancreas or extrahepatic biliary system

Exclusion Criteria:

• Uncorrectable coagulopathy (INR > 1.5)
• Uncorrectable thrombocytopenia (platelet < 50,000)
• Decline to participate in the study and sign the informed consent form
• Cystic lesions.

The pathologists who assess the FNB specimens are blinded on the needle type