IgG4-positive plasma cells in cutaneous Rosai-Dorfman disease: An additional immunohistochemical feature and possible relationship to IgG4-related sclerosing disease

Background: Cutaneous Rosai-Dorfman disease (CRDD) shares the histopathological features of abundant plasma cells and stromal fibrosis with IgG4-related sclerosing disease. The possible role of IgG4+ plasma cells in CRDD was investigated. Methods: Twelve cases of CRDD were reviewed, and their lesions were immunostained with anti-IgG4 and anti-IgG antibodies. The number of IgG4+ and IgG+ plasma cells and their ratios were estimated. Serum IgG4 and IgG concentrations were measured in two recent cases. Results: Many IgG4+ and IgG+ plasma cells were found in all 12 cases. IgG4+ plasma cells ranged from 21 to 204 per high-power field (HPF) (mean 117/HPF), and IgG+ plasma cells ranged from 114 to 759/HPF (mean 349/HPF). All cases had more than 30 IgG4+ cells/HPF, except one case. The IgG4/IgG ratio ranged from 16% to 51% (mean 34%). Serum IgG4 concentration and serum IgG4/IgG ratio were increased in one recent case. Various degrees of stromal fibrosis were present in all cases. Conclusions: The presence of many IgG4+ plasma cells and stromal fibrosis suggests that CRDD may be related to IgG4-related sclerosing disease. Many IgG4+ plasma cells is another feature of CRDD, and serum IgG4 may be elevated. Kuo T-t, Chen T-C, Lee L-Y, Lu P-H. IgG4-positive plasma cells in cutaneous Rosai-Dorfman disease: an additional immunohistochemical feature and possible relationship to IgG4-related sclerosing disease.