High lesional expression of IL-17F is associated with progressive disease. Kaplan-Meier analyses of (A) disease progression and (B) disease-specific survival in the Boston historic cohort of CTCL patients (n = 60) stratified according to IL-17F mRNA expression in lesional skin. Seventeen patients were classified as IL-17F+ and 43 patients as IL-17F−. The Kaplan-Meier disease progression analysis was performed taking into account multiple progression events for each patient.