IL17F and histiocytic sarcoma: Hidradenitis suppurativa (HS) has shown a T-helper 17 cell- (TH17-) skewed cytokine profile in inflamed HS skin, based on intracellular cytokine staining, with the ratio of TH17 to regulatory T cells dysregulated in favor of TH17 cells (identified by flow cytometry using antibody to IL-17A or IL-17F).