Immunological characteristics of IgG4-related Kuttner tumors

Immunoglobulin G4-related disease (IgG4-RD) has recently been well recognized and Kuttner tumor is known to be a chronic sclerosing sialadenitis, representing the focal manifestation of IgG4-RD, in the submandibular gland (SMG). This study is to evaluate the immunologic features of IgG4-related Kuttner tumor in the SMG. We retrospectively chose 13 patients who were confirmed as having Kuttner tumor by surgical biopsy between May 2012 and January 2019. The fine-needle aspiration cytology, serum antibody levels (anti-Ro antibodies, anti-La antibodies), IgG serum levels (total IgG and IgG4), and immunohistochemical findings for IgG and IgG4-positive plasma cells were reviewed. The cytologic results found that 7 of the 9 cases were reported as chronic sialoadenitis, and the other 3 as benign lymphoproliferative lesion. The serum levels of autoantibodies, Sjögren-syndrome-related antigen A/Ro-Ab and Sjögren-syndrome-related antigen A/Ro-La, showed all normal values of serum level. The serum level of IgG was increased in only 4 among the cases. However, the IgG4 levels were significantly increased in 11 among the cases. In all the patients who received resection of SMG, immunohistochemical findings showed all positive for IgG4-RD, with elevated numbers of IgG and IgG4-positive plasma cells. The evaluation of IgG4 serum level should be very informative for the diagnosis of this tumor before surgery. Fine-needle aspiration cytology with ultrasound guidance are not conclusive in this study. The immunological study including IgG4 serum level should be required for proper diagnosis and treatment, with clinical features of the Kuttner tumor. The level of evidence was IV.