The mucin-type O-glycome in cancer aberrantly expresses the truncated glycans Tn (GalNAca1-Ser/Thr) and STn (Neu5Aca2,6GalNAca1-Ser/Thr). However, the role of Tn and STn in cancer and other diseases is not well understood. Our recent discovery of the self-binding properties (carbohydrate-carbohydrate interactions, CCIs) of Tn (Tn-Tn) and STn (STn-STn) provides a model for their possible roles in cellular transformation. We also review evidence that Tn and STn are members of a larger family of glycan tumor antigens that possess CCIs, whichmay participate in oncogenesis. [ABSTRACT FROM AUTHOR]