Background/Purpose: Immunoglobulin G4-related disease (IgG4-RD) is a recently defined entity characterized by a diffuse or mass forming inflammatory reaction rich in IgG4-positive plasma cells.  Due to the fact that IgG4-RD was only fully described in the past decade, the epidemiology and prevalence of this disease is still not understood. It is likely that many pathology specimens prior to this time period were not recognized as IgG4-RD.The purpose of this study is to identify IgG4-RD in a by retrieving archived pathological slides originally diagnosed as idiopathic sclerosing masses, fibrosis or chronic inflammation in our tertiary care center.

Methods: This is a retrospective review of archived pathological slides at Westchester Medical Center from the years 2005-2015.We initially retrieved 105 cases using various search criteria from the Pathology database. Of these, 23 cases were included in this study, which fulfilled our final inclusion criteria of biopsy-proven idiopathic sclerosing masses, fibrosis and/or chronic inflammation. Immunohistochemical stains were performed on these specimens including IgG4. In this study we defined IgG4–RD as immunohistochemistry (IHC) > 10 IgG4+ plasma cells/ HPF and IgG4+/IgG ratio>40%, as well as the presence of characteristic histopathology architecture (dense lymphoplasmacytic infiltrate, storiform fibrosis and obliterative phlebitis) ^1,2. Other epidemiological data obtained were age, gender, organ involved and original tissue pathology diagnosis.  

Results: Thirty-four percent of the biopsies (n=8/23) were reclassified as IgG4-RD.  The most common original histological diagnosis for the eight reclassified specimens was chronic sialadenitis (Table Image) with submandibular gland most frequently involved, followed by parotid gland and retroperitoneal mass. The reclassified specimens were more common in females (5/8) and those above ages 60 (5/8).

Conclusion: This is the only known reported retrospective review study of archived pathological slides for IgG4-RD. The results highlight the ability to reconsider diagnosis, if needed, by performing appropriate immunohistochemical analysis on archived specimens to identify IgG4-RD. Chronic sialadenitis was the most common mimicker of IgG4-RD. Reference : 1. Deshpande V, et al. Consensus statement on the pathology of the IgG4-related disease. Modern Pathol. 2012; 25:1181–92 2. Khosroshahi A, et al. International Consensus Guidance Statement on the Management and Treatment of IgG4-Related Disease. Arthritis & Rheumatology, 2015; 67: 1688–1699.