MUC1 and cancer: Increased levels of MUC1 expression and its altered glycosylation have been associated with cancer progression and metastasis that correlate with poor prognosis and high mortality [3,60,61,62] Metastasis is a multi-step process during which cancer cells leave the primary tumor site, infiltrate into the adjacent tissue by degrading the extracellular matrix, enter into blood stream wherein they are recognized as circulating tumor cells, and extravasate and colonize a secondary site.