Lymphomas that occur in the setting of IgG4-related disease (IgG4-RD) are uncommon. Most reported cases derive from Asia and are MALT lymphomas occurring in orbital IgG4-RD. The spectrum of lymphomas among IgG4-RD patients in the Western world remains poorly defined. The aim of this study was to report our experience with lymphomas occurring in IgG4-RD. Eight cases were identified from the pathology and consultation files. The median age was 61 years (range 22-68) at IgG4-RD diagnosis and 63.5 years (range 33-79) at lymphoma diagnosis, with a M:F ratio of 4:4. The diagnosis of lymphoma and IgG4-RD was concurrent in three cases and asynchronous in five (interval 4.3-16.4 years). Concurrent cases included a MALT lymphoma and a diffuse large B cell lymphoma (DLBCL) occurring with IgG4-related sialadenitis and a follicular lymphoma occurring with orbital IgG4-RD. Asynchronous cases included a lymphoplasmacytic lymphoma with large cell transformation and intervening IgG4-related pancreatitis, a MALT lymphoma after lacrimal IgG4-RD, two DLBCLs after multiorgan IgG4-RD, and a DLBCL after IgG4-related sialadenitis. Our findings suggest that lymphomas in IgG4-RD are more varied in location and type than the experience reported from Asia to date. Pathologists should be aware of the potential for lymphoma to develop in patients with IgG4-RD and should have a high degree of suspicion when lymphadenopathy or extranodal masses persist despite appropriate therapy for IgG4-RD. The co-occurrence of IgG4-RD and lymphoma that is reported here and previously suggests a possible etiologic association.
Keywords: IgG4-RD; IgG4-related disease; Lymphoma.