Study objective: To describe the microflora characteristics of the pancreatic solid lesions via the tissue acquired via the endoscopic ultrasound-guided fine needle aspiration/biopsy (EUS-FNA/B).

Study design: This is a prospective observational study.

This is a prospective observational study. Patients who need EUS-FNA/B for diagnosis of pancreatic solid lesions (pancreatic cancer, chronic pancreatitis, and autoimmune pancreatitis, etc)will be successively included in this study. The EUS-FNA/B procedures will be accomplished in the standard way after the puncture site is washed with 20ml sterile saline for three times. The remaining fresh tissue after sufficient specimen collected for the diagnosis will be stored in - 80℃ fridge. DNA is extracted from all samples using the suitable kit and V4 16S rRNA gene sequencing is performed on all samples. The investigators ran "Decontam" (Davis NM, et al. Microbiome 2018;6:226) in order to identify and remove contaminant DNA sequences from the dataset. And the microbiome is analyzed with the standard methodology. The investigators tend to describe the microflora characteristics of pancreatic solid lesions and try to compare the differences between cancer and benign diseases.

This study will carry out in two stages: the preliminary stage, 10 patients will be included. If the technic success rate (successful extraction of DNA and sequencing of 16s rRNA after bioinformatical removal of potential DNA contaminations via the use of 'Decontam') is high than 50%, the successive inclusion progress [the main stage] will last for one year.

Inclusion Criteria:

• Patients who need EUS-FNA/B for diagnosis of pancreatic solid lesions.
• Age ≥ 18 years and < 80 years.

Exclusion Criteria:

• Including but not limited to: poor general conditions, severe cardiopulmonary disease, difficult to tolerate EUS examination; coagulation dysfunction; platelets <50×10^9/L

Patients who need EUS-FNA/B for diagnosis of pancreatic solid lesions.