According to the distribution of gene variation in the population, five genes that could cover the largest population were screened, namely, TP53, APC, KRAS, BRAF and ATM. Mutations of them covered 97.55% (513/518) of TCGA population and 83.02% (44/53) validation patients (Fig. 2a), and can be used to distinguish between cancer and paracancer. Here, BRAF is linked to cancer.