The FDA for the first time approved a cancer treatment based on specific genetic biomarker, rather than location in the body where the tumor originated. KEYTRUDA®, an anti-PD1 monoclonal antibody was granted accelerated approval for treatment of adult and pediatric patients with unresectable or metastatic, MicroSatellite Instability-High (MSI-H) or MisMatch Repair deficient (dMMR) solid tumors that have progressed following prior treatment and who have no satisfactory alternative treatment options or with MSI-H or dMMR ColoRectal Cancer that has progressed following treatment with a Fluoropyrimidine, Oxaliplatin, and Irinotecan. MMR gene deficiency can be detected by ImmunoHistoChemistry and MSI testing is performed using a PCR based assay.