CD44 is a ubiquitously expressed receptor for hyaluronan and exerts control over cell growth, migration, and tumor progression. With variable N and O-glycosylation and splicing within the stalk, CD44 can range from 80 to 200 kDa. CD44 binds hyaluronan and other ligands within the extracellular matrix and can function as a “platform” for growth factors and metalloproteinases. It can function as a co-receptor that modifies activity of receptors including Met and the ErbB family tyrosine kinases. The intracellular domain of CD44 links the plasma membrane to the actin cytoskeleton via the ERM proteins, ezrin, radixin and moesin.