Hyaluronan (HYA) plays a particular role in cancer cell microenvironment. A component of the desmoplasia. HYA is associated to other macromolecules and contributes to the net structure of the matrix. Cancer cells exhibit binding sites (CD44, RHAMM) for HYA. The cell adhesion to HYA can influence the cell motility and different factors could interplay to facilitate cell detachment from HYA. HYA protects cancer cells against immune cell attack. Serum HYA is often increased in metastatic patients.