CD163 and immunoglobulin G4-related sclerosing disease: Recently, several studies reported that M2 macrophages contribute to fibrosis formation by producing CC-chemokine ligand-18 in IgG4-RD.[5,6] Consistent with these findings, case 1 in the present study showed massive infiltration of CD163+ M2 macrophages in the area affected by storiform fibrosis associated with IgG4-related FM.