These observations suggest that, while loss of functional Cosmc by mutation, deletion, or hypermethylation contributes to Tn expression in some cancer cell lines and certain types of malignancies (such as pancreatic cancer) observed so far [13, 17, 23, 28, 29], other mechanisms do exist to cause revertible expression of the Tn antigen. This evidence concerns the gene C1GALT1C1 and familial pancreatic carcinoma.