MUC1 is a tumor-associated transmembrane antigen expressed at low levels on the apical surface of ductal epithelial cells in several organs, and overexpressed in the majority of adenocarcinomas and their precursor lesion, where its tandem repeat region is reported to have truncated O-glycans [16,17,18,19,20]. The gene discussed is MUC1; the disease is adenocarcinoma.