In a 2019 study wherein 18 218 tumor samples underwent next-generation sequencing, Lieu et al7 found that among patients with tumors exhibiting microsatellite stability, those with YO CRC (uniquely defined as cancer diagnosed at age <40 years in this study) differed from those with LO CRC, with a lower frequency of APC, KRAS, BRAF, and FAM123B sequence variants and a higher frequency of TP53 and CTNNB1 variants. The gene discussed is KRAS; the disease is cancer.