PTGS2 and colorectal carcinoma: In addition to the above-mentioned genes frequently present in MSI-high CRC, other genes are present at a lower frequency (around 20%) including mutations in the MMR genes hMSH3 (36.5%) and hMSH6 (17.5%), Insulin Growth Factor Type 2 Receptor (IGFIIR) (22%), BLM gene (16%), PIK3CA (15%), G protein-coupled receptor of Prostaglandin-endoperoxide synthase 2 (PTGS2) (33%) and Cyclin D1 gene (28%) [86–90].