Although majority of the studies used immunohistochemistry to evaluate the expression of EGFR, HER2, and HER3 in CRC, some previous investigations used other technologies, e.g. fluorescence in situ hybridization (FISH), next-generation sequencing (NGS), silver in situ hybridization (SISH), reverse transcription-polymerase chain reaction (RT-PCR), SNP-array, and microarray. This evidence concerns the gene EGFR and colorectal carcinoma.