IL17A and histiocytic sarcoma: The pathogenesis of HS is multifactorial and involves complex mechanisms of innate immune system: infiltration of macrophages and neutrophils, production of pro-inflammatory interleukins (IL-1, TNF-α, IL-17, IFN-γ) and B-cell mediated processes associated with antibodies production and dermal lymphatic structures (2, 5, 6).