S100P is a new member of S100 family, named after its initial separation from placenta. It is widely distributed in normal tissues, including heart, brain, liver, lung, bone marrow, placenta, bladder, spleen, gastrointestinal tract, peripheral blood leukocytes, etc. Abnormal expression in tumors plays an important role in tumor growth, proliferation, invasion and metastasis through various signal pathways. S100P was negative in benign pancreatic duct and normal bile duct, but highly expressed in pancreatic ductal adenocarcinoma and cholangiocarcinoma. S100P is also a specific marker for bladder cancer and urothelial carcinoma.