Fig. 4

(A) At low magnification, the lymphatic sinuses are open, the lymphatic follicles are visible, the germinal centres are narrowed, and numerous mature plasma cell infiltrates are seen between the follicles in a lamellar pattern (×100); (B) The infiltrating plasma cells are cytoplasm-rich, dichromatophilic, with large round, deviated nuclei and wheel-like chromatin under high magnification (×400); (C, D) CD38 and CD138 immunohistochemical staining showed a large number of positive plasma cells between the follicles; (E) Immunoglobulin (IgG) positive plasma cells could be seen by immunohistochemical staining; (F) IgG4-positive plasma cells could be seen by immunohistochemical staining; The IgG4/IgG ratio was greater than 40%