Mutations that lead to EGFR overexpression (known as upregulation or amplification) have been associated with a number of cancers, including adenocarcinoma of the lung (40% of cases), anal cancers,[16] glioblastoma (50%) and epithelian tumors of the head and neck (80-100%).[17] These somatic mutations involving EGFR lead to its constant activation, which produces uncontrolled cell division.[18] In glioblastoma a specific mutation of EGFR, called EGFRvIII, is often observed.[19] Mutations, amplifications or misregulations of EGFR or family members are implicated in about 30% of all epithelial cancers.[citation needed]