Many carcinoma-associated markers are glycoconjugates whose expression undergoes temporal or spatial regulation. Mucin-1 (MUC1), discovered through monoclonal antibody technology, is a well-documented example of such a molecule and influences numerous pathophysiological behaviors, such as the invasion and metastasis of carcinoma cells. Levels of MUC1 expression in carcinomas correlate with the clinical stage of the cancer and inversely correlate with the survival prospects of patients. The MUC1 immune response is known to provide a protective host defense mechanism against cancer. The multiple functions of MUC1 in carcinoma-host interactions are believed to be dependent on the polymorphic nature of MUC1, particularly its glycosylation status.