CD1A and histiocytic sarcoma: HS is a complex disorder, with ~ 25% of patients developing autoinflammatory complications consisting of unexplained fevers, persistently elevated inflammatory markers, and unusual lymphadenopathies, with infiltrating CD68+, S100+, and CD1a− histiocytes, resembling the immunophenotype found in Rosai-Dorfman disease (RDD).