IgG4-positive plasma cells in nonspecific sialadenitis and sialolithiasis.

Chronic sclerosing sialadenitis is commonly regarded as a manifestation of IgG4-related disease. We previously found that a high IgG4 expression or IgG4-related disease could accompany nonspecific sialadenitis, whereas chronic sclerosing sialadenitis was not directly associated with IgG4-related disease. Our previous findings lead us to hypothesize that these inflammatory conditions of the submandibular gland signify a continuous progression of disease rather than different disease entities. We, therefore, aimed to determine the presence of IgG4-positivity and genuine IgG4-related disease in a cohort of 165 submandibular gland specimens from patients who underwent surgery due to chronic nonspecific sialadenitis or sialolithiasis. To do so, we re-evaluated histopathological features and divided samples into three groups: (A) nonspecific sialadenitis without known sialolithiasis, (B) sialadenitis with sialolithiasis, and (C) sialolithiasis without sialadenitis. We performed immunohistochemical staining for IgG4, IgG, and CD31, and assessed the Boston consensus statement criteria for IgG4-related disease in IgG4-positive samples. We also reviewed patient records and supplemented follow-up data with a questionnaire among patients with IgG4-positive samples. IgG4-positive plasma cells (range 1-344) were found in 131 samples. Among these, 19 samples were classified as IgG4-positive (≥70 IgG4-positive plasma cells/high-power field). Two IgG4-positive samples were histologically highly suggestive of IgG4-related disease, but only one had a clinically confirmed diagnosis of IgG4-related disease. Our results indicate that patients with sialadenitis and sialolithiasis often present with IgG4-positive lymphoplasmacytic infiltrates, but exceedingly rarely present with genuine IgG4-related disease. In sialolithiasis without sialadenitis, IgG4-positive plasma cells are often absent or appear in small numbers. These results support our hypothesis of a continuum of disease, and indicate that progressive inflammation of the submandibular gland leads to the development of more specific pathological features over time.

Sclerosing sialadenitis of the submandibular gland is rarely an immunoglobulin G4-related disease in the Finnish population.

Chronic sclerosing sialadenitis may represent one of many manifestations of an immunoglobulin G4-related disease. However, existing studies typically consist of small patient cohorts rarely conducted in Western populations. The clinical behavior of chronic sclerosing sialadenitis, including follow-up data, warrants further study. Thus, we aimed to determine whether chronic sclerosing sialadenitis always presents as IgG4-related disease or associates with autoimmune diseases and to determine which additional examinations patients may require. Between 2000 and 2017, 51 patients undergoing submandibular gland resection within the Helsinki University Hospital area were diagnosed with chronic sclerosing sialadenitis. We re-evaluated all specimens and performed immunostaining for IgG4. IgG and CD31 stainings were performed for IgG4-positive specimens. IgG4-related disease diagnosis was defined by the Boston consensus statement criteria. We revised clinical data, distributing a follow-up questionnaire to patients to register symptoms of IgG4-related disease or autoimmune disease during follow-up. The chronic sclerosing sialadenitis criteria were fulfilled in 34 patients, whereby 17 were diagnosed as non-sclerosing chronic sialadenitis. In 19 cases, a sialolith associated with a salivary gland lesion. In total, 12 of 51 cases were recognized as IgG4-positive, while two met the criteria for IgG4-related disease. These two cases belonged to the non-sclerosing chronic sialadenitis group, and both involved other organs. The histopathological features between chronic sclerosing sialadenitis and non-sclerosing chronic sialadenitis overlapped regarding the degree of fibrosis and inflammatory infiltrates. In the Finnish population, chronic sclerosing sialadenitis of the submandibular gland does not appear to present as IgG4-related disease. Non-sclerosing chronic sialadenitis can associate with IgG4-related disease. A histopathological distinction between chronic sclerosing sialadenitis and non-sclerosing chronic sialadenitis is not always unequivocal and the presence of a sialolith does not exclude IgG4-positivity. Therefore, immunostaining for IgG4 should be performed when dense plasma cell infiltration is present in either non-sclerosing chronic sialadenitis or chronic sclerosing sialadenitis.