Clinical characteristics and outcomes of IgG4‐positive marginal zone lymphoma: Systematic scoping review

Abstract Immunoglobulin G4 (IgG4)‐positive marginal zone lymphoma (MZL) is rare and undefined. It is unclear whether IgG4‐positive MZLs have as favorable an outcome as MZLs in general. Also, correlation with IgG4‐related disease (IgG4‐RD) and IgG4‐positive MZLs is unknown. Following the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses extension for scoping reviews, we searched MEDLINE and EMBASE for all peer‐reviewed articles using keywords including“IgG4” and “marginal zone lymphoma” from their inception to February 20, 2022. Twenty‐two articles, including six observational studies and 24 cases from 16 case reports and case series, were included. Only one study had a comparative group, and the other five were exploratory observational studies. IgG4‐positive MZLs commonly occurred in males (83.3%). It primarily involved ocular adnexa (41.7%) and skin (29.2%). Only 29.2% had concurrent IgG4‐RD, and no expiration was noted. While most cases were treated with excision, resection, or clinical observation, 21.7% received rituximab‐cyclophosphamide, doxorubicin, vincristine, and prednisone as a first‐line treatment. This systematic review summarizes the current understanding of the characteristics of IgG4‐positive MZLs. While there seems to be IgG4‐RD‐related and de novo IgG4‐positive MZLs, future research needs to clearly define MZL with polyclonal IgG4‐positive cells and IgG4‐producing lymphoma. Further studies are critical to clarifying long‐term prognosis and optimal surveillance planning.