Expression of blood group antigens in bladder cancer: current concepts.

Blood group antigens are a group of carbohydrate structures bound to membrane lipids or proteins of erythrocytes and certain epithelial tissues including urothelium. The Lewis antigens are structures that are genetically and biochemically related to the ABO blood group. The ABO and Lewis blood group systems are differentially expressed in the normal urothelium of "secretors" versus "nonsector" individuals. The normal urothelium of "secretors" is rich ABH, Leb, and Ley antigens while the urothelium of "nonsecretors" does not express these antigens. Therefore, deletion of ABH antigens, commonly noted in TCC, can only be reliably ascertained in "secretor" individuals. Neoexpression of the Lewis X antigen (which is absent in normal urothelium) is noted in over 85% of TCC regardless of tumor stage and grade. Immunocytological detection of the Lewis X antigen on exfoliated bladder epithelial cells enhances the detection of urothelial tumor cells, particularly from low grade and low stage neoplasms.