IGHA1 and histiocytic sarcoma: Regardless, as reported by Frew et al., (i) tertiary lymphoid organs (TLOs), where autoreactive B cells develop and interact with T cells, have been identified in HS, (ii) an upregulation of immunoglobulin (Ig)G3/IgG1, kappa light chains, lambda light chains, IgD, and IgA1 in lesional HS was demonstrated, and (iii) B cells may amplify the inflammatory response and contribute to the fibrotic process (via IL-6 and transforming growth factor-β, TGF-β) in HS lesions [90].