CTCL stage IV patients harboring a RAS mutation show reduced life expectancy. Kaplan-Meier curve: Comparison of survival of mutant (all stage IV), nonmutant stage IV patients (P = .041), and nonmutant stage I to III patients (P = .001). P values were determined by Student t test (2-tailed) comparing individual group versus the mutant patient samples group. Similarly, the 2 nonmutant groups, when considered together, showed significance for prolonged survival compared with the mutant patient samples group (P = .017, 2-tailed Student t test). Considered are time span from first diagnosis to date of death or last visit, when applicable, respectively.