EGFR and cancer: Molecular pathogenesis of CRC represents a prototypal model of carcinogenesis and cancer progression and it is sustained by aberrant modulation of few signaling pathways: WNT–β–catenin signaling pathway, the TGF-β1 signaling pathway, the epidermal growth factor receptor (EGFR)–mitogen activated protein kinase (MAPK) pathway, and the PI3K pathway.