Summary of the study design. (A) In study design 1, spatial transcriptomic analysis based on the morphology of MF (patch-, plaque-, and tumor-stage MF) was conducted and progression signature that significantly and continuously increased in expression during progression was discovered. (B) Next, spatial transcriptomic analysis based on the clinical course was performed among patients with stage I MF. (C) In study design 3, IHC staining was performed on a new patient data set, including patch-stage MF, progressive plaque-stage MF, indolent plaque-stage MF, and tumor-stage MF. EORTC, European Organization of Research and Treatment of Cancer; ISCL, International Society for Cutaneous Lymphomas; yr, year.