CD44 and neoplasm: Cluster of Differentiation 44 (CD44) is a multistructural and multifunctional transmembrane glycoprotein, which can be used as a receptor for hyaluronic acid and many other extracellular matrix components, as well as for a variety of growth factors and cytokines.[5] Many studies have shown that CD44 is involved in many key processes of cells, including cell growth, reproduction, differentiation, adhesion and migration.[6,7] CD44 is also a common tumor marker, which is closely related to the proliferation, migration and invasion of tumor cells, and participates in tumor-related angiogenesis.