Targeted sequencing of individual genes to guide therapy has become the standard of care for several different cancer types, including colorectal cancer (KRAS, BRAF, and NRAS), lung cancer (KRAS and EGFR), melanoma (BRAF), GI stromal tumor (KIT), and gliomas (IDH1 and IDH2). The gene discussed is KRAS; the disease is central nervous system cancer.