Besides melanoma, also other invasive and metastatic tumors (e.g. colon and breast carcinoma) present an aberrant expression of α2,6-sialic acids mainly because of the overexpression of ST6Gal1 sialyltransferase, which adds terminal sialic acid moieties on N-linked glycans [14]. The gene discussed is ST6GAL1; the disease is breast carcinoma.