KRAS and colorectal carcinoma: Suzuki et al. have shown a variable level of ITH using deep-targeted NGS followed by ultra-deep amplicon sequencing through the analysis of 4 different CRC patients investigated at the level of various tumor regions; different tumor regions shared mutations in driver genes, such as APC, KRAS and TP53. However, in addition, many mutations were observed only at subclonal levels and in many instances their detection was only revealed by an ultra-high-depth sequencing approach [54].