EGFR stands for epidermal growth factor receptor. It is a transmembrane protein acting as a tyrosine kinase receptor for epidermal growth factor ligands, which are associated with promoting cell division and proliferation. When epidermal growth factor binds to the receptor, it becomes activated and undergoes dimerization and autophosphorylation.
A mutation could occur making the receptor overactive. That is, it does not require ligand binding to become activated, meaning it is always in an "on" state. This would lead to uncontrolled proliferation, a hallmark of cancer.
