Mucin 1 (MUC1) is a multistructural and multifunctional protein that is involved in regulating diverse cellular activities. This strongly glycosylated transmembrane protein forms a mucous gel on the surface of epithelial cells that protects the cells from injury. MUC1 acts as a signaling molecule and transcription factor modulating metabolism and resistance to bacterial-induced inflammation. This article presents a review of the relationship between structural and functional changes of the MUC1 and the characteristics of cancer cells. The alteration in MUC1 expression level, a number of structural forms, protein glycosylation and localization occurs in cancer cells. These alterations lead to metabolic reprogramming associated with proliferation, resistance to hypoxia and angiogenesis which affects the survival of cancer cells. Furthermore, cancer cells can take advantage of MUC1 interaction with adhesion molecules for invasion and metastasis. Thus, MUC1 plays a key role both in the homeostasis of epithelial cells and in cancer progression. Understanding the role of MUC1 expression in tumor cells survival is important for the development of new monitoring and therapeutic approaches for the treatment MUC1 positive maligancies.