HS lesions had a greater amount of regulatory T cells and inflammatory cytokines from T helper type 17 (Th17) T cells producing IL-17 cytokines. These Th17 cells also produced a variety of other proinflammatory cytokines (GM-CSF, IL-22, IFN-γ) in addition to TNF. Anti-TNF therapy significantly reduced the amount of Th17 cells in lesions, bringing the ratio of Th17 T cells to regulatory T cells closer to what is expected in a healthy patient’s skin. Here, CSF2 is linked to histiocytic sarcoma.