Abstract
The antigens of the ABO system are expressed on red blood cell membranes as well as on the surface of several other normal and pathological cells and tissues. Following the first clinical observations more than 60 years ago, the role of ABO blood group in cancer biology has been intensely studied by several investigators, and it is now widely recognised that ABO antigens are associated with the risk of developing several types of tumours, namely pancreatic and gastric cancers. However, whether this association also affects the clinical outcome of cancer patients is less certain. In this narrative review, based on literature data, we discuss the role of ABO blood types as prognostic biomarkers in different types of cancers. The current knowledge of the underlying pathogenic mechanisms of the association is also analysed.