The trefoil factor (TFF) family includes three members : TFF1 also called pS2, TFF2 or spasmolytic peptide (SP) and TFF3 or intestinal trefoil factor (ITF). TFFs are associated with mucin-secreting epithelial cells and play a crucial role in mucosal defense and healing. In case of mucosa aggression (due to bacteria, virus or medication), inflammatory diseases and ulcerous pathology, they are involved in epithelium restitution and regeneration. In comparison with the other TFFs, pS2/TFF1 has particular functions. Notably, it acts like a suppressor gene for gastric tumors. Evidence of pS2/TFF1 overexpression has been found in a range of carcinomas (breast, bowel, prostate, pancreas, thyroid, lung...). In breast cancer, pS2/TFF1 overexpression contributes to a favorable prognosis. Moreover, it is a predictive factor of hormonotherapy response.