FOXP3 and mycosis fungoides: As a result of these genetic alterations and other environmental changes or unknown factors, the phenotype of the neoplastic cells in MF may harbor markers that characterize different normal T-cell populations, including TFH (PD1, CXCL13, ICOS1, etc.), Treg (CD4, CD25, FOXP3), TH1, TH2 and TH17 cells.