TPBG, also known as 5T4, is a type I transmembrane glycoprotein that may be involved in cell adhesion, which is an antagonist of Wnt/β-catenin signalling pathway. TPBG is expressed on trophoblasts, tumor cells, ovarian cuboidal epithelium and embryonic stem cells, and impacts cell adhesion and motility. TPBG has very limited expression in normal tissue but is widespread in malignant tumours throughout their development. Its confined expression appears to give TPBG the potential to be a target for T cells in cancer immunotherapy.