EGFR and colorectal carcinoma: The epidermal growth factor receptor (EGFR) is a tyrosine kinase (TK) transmembrane receptor that is constitutively expressed in tissues of epithelial origin and is overexpressed in a variety of solid tumors including colorectal carcinoma, non-small cell lung carcinoma, renal cell carcinoma, ovarian, head and neck, prostate, breast, and pancreatic carcinomas [6,7].