Figure 3C. Parotid tumor and enlarged lymph nodes 13 months before the diagnosis of immunoglobulin (Ig) G4-related disease. Low-power magnification shows (a) an enlarged lymph node with increased numbers of lymphoid follicles and (b) the parotid gland with an encapsulated cystic tumor (HE, ×10). The lymphoid follicles (c) in the lymph node show increased numbers of plasma cells (inset), especially at the border between the germinal center and mantle zone (HE, ×200). (d) The parotid tumor was a so-called cystadenolymphoma (Warthin tumor), also with increased numbers of plasma cells (not shown) (HE, ×200). Immunohistochemistry again shows significantly increased numbers of IgG4-positive plasma cells (e) relative to IgG-positive forms (f) (immunoperoxidase, ×200).