The investigators are going to explore the diagnostic and prognostic value of circulating tumor cells and exosomes extracted from the portal venous blood obtained with endoscopic ultrasound in pancreatic cancer patients.

As the prognosis of pancreatic cancer, a kind of malignant tumor, remains poor due to the low diagnostic rate at the early stage, there is still a significant clinical need to determine individualized tumor molecular profiles and personalized risk for recurrence. Circulating tumor cells (CTCs) and exosomes from patients with primary tumors may hold promise in serving as an informative biomarker to address this clinical need. Here in this study, the investigators are going to explore the feasibility and safety of sampling portal venous blood via endoscopic ultrasound (EUS), and detect portal venous CTCs and analyze mRNA markers of exosomes by RNA-seq. The investigators aim to explore the potential molecular mechanisms in tumor microenvironment and mechanisms of drug resistance.

Inclusion Criteria:

1. Aged from 18 to 80 years-old
2. Suspected pancreatic masses and referred for EUS-FNA for pathology diagnosis
3. Written informed consent

Exclusion Criteria:

1. Patients who have received adjuvant chemotherapy and other anti-tumor treatments
2. Severe heart, lung, liver, kidney insufficiency, or severe bleeding disorders, severe coagulopathy or local/systemic infections, other critical illnesses
3. Women who are planning to become pregnant or are pregnant or breast-feeding

Patients suspected to have pancreatic masses who are going to receive EUS-FNA operations for diagnostic purposes.