Pancreatic cancer is a disease with an extremely poor prognosis. Such poor results are largely due to a high incidence of local or peritoneal recurrence even after curative R0 resection. If occult microscopic metastasis or residual cancer could be predicted correctly and identify the high risk of peritoneal recurrence, we may have chance to treat these patients by different multimodal locoregional or adjuvant therapy to improve the treatment outcome.

The purpose of this study has three specific aims: (1) to determine the relationship between peritoneal washing cytology (PWC) results and clinicopathologic parameters of pancreatic cancers, (2) to identify the predictive value of PWC and postoperative drainage cytology on the peritoneal recurrence or outcomes, (3) to dissect the molecular mechanism of peritoneal recurrence, especially on the PWC-inducing peritoneal seeding process.

Inclusion Criteria:

• Patients with pancreatic cancers, other non-ductal pancreatic cancers , and benign pancreatic tumors (as negative control population) operated in Surgical Department after IRB proof and receiving patients' informed consent.

Exclusion Criteria:

• Pregnant women

operated in Surgical Department of National Taiwan University Hospital