FUCA1 and neoplasm: Among the glycosyl linkages found in glycan-based tumor-associated antigens, α1,3fucosyl residues attached to GlcNAc residues are one of the most common structures expressed in tumor cells with very abundant and aberrant existence in plasma and/or serum as LeX (Galβ1,4[Fucα1,3]GlcNAc), sialyl LeX (NeuAcα2,3Galβ1,4[Fucα1,3]GlcNAc), sialyl LeX-i (NeuAcα2,3Galβ1,4[Fucα1,3]GlcNAcβ1,3Galβ1,4GlcNAc), poly LeX ((Galβ1,4[Fucα1,3] GlcNAc)n) and LeY (Fucα1,2Galβ1,4[Fucα1,3]GlcNAc) antigens [1, 22–24] (Fig 1).