Tumour-associated changes such as the Tn antigen and other changes in O-glycosylation have been found to be immunogenic and present on a variety of proteins, e.g. CD43 in T-cell leukaemia cells [1], MUC-1 in colon cancer [2], CD44 in breast carcinoma [3] and nucleolin in melanoma [4]. The gene discussed is MUC1; the disease is breast carcinoma.