KRAS and colorectal carcinoma: Fourth, PTEN mutations selectively occur within CRC subsets defined by the presence of specific driver mutations in MT-L tumors, including tumors driven by BRAF, BRAF + TP53, APC + KRAS, or APC mutations; in contrast, PTEN mutations are least likely to occur in tumors bearing APC + TP53, TP53, KRAS + TP53, KRAS, or APC + KRAS + TP53 mutations (P < 2.2e−16), or lacking mutations in any of these genes.