These results suggest that mAbs, such as ACH18 and FH4, are selective for internal epitopes presented by polymeric Lex structures, while anti-monomeric Lex mAbs (anti-SSEA-1, FH3 etc.)react with the terminal Lex trisaccharide presented by mono-, di- and trimeric Lex glycolipids on cancer cells and tissues [11,25]. This evidence concerns the gene FUT4 and cancer.