An established carbohydrate-based cancer marker is the Thomsen-Friedenreich (TF) antigen (Galβ1-3GalNAcα), which is typically found O-linked to serine or threonine residues. The TF antigen (also known as T antigen) has been associated with several human carcinomas, including those found in the pancreas, colon, and breast, and on this basis has been referred to as a pan-carcinoma marker. TF antigen is concealed from the immune system in normal adult tissues as a result of extension with larger glycan chains. In cancer, the cellular glycosylation machinery may be disrupted, leading to truncation of these chains and exposure of the TF antigen.