Immunoglobulin G4 (IgG4)-Positive Ocular Adnexal Mucosa-Associated Lymphoid Tissue Lymphoma and Idiopathic Orbital Inflammation

Purpose: To report clinical and pathological characteristics of idiopathic orbital inflammation and ocular adnexal mucosa-associated lymphoid tissue (MALT) lymphoma with immunoglobulin G4 (IgG4)-positive plasma cells. Methods: A retrospective histopathological review and clinical case series. A total of 51 biopsy samples from January 2005 to December 2015 were used in this study, including 21 cases of biopsy-confirmed idiopathic orbital inflammation and 30 cases of biopsy-confirmed ocular adnexal MALT lymphoma. Most cases of ocular adnexal lymphoma were conjunctival tissue. Retrospective immunohistochemical studies were performed to estimate the IgG4 and IgG4/IgG ratios. Histopathologic features, demographic and clinical data, radiologic findings, treatment, and follow-up information for each patient were analyzed. Results: Among idiopathic orbital inflammation, 6 (28.6%) of the 21 patients were diagnosed as "probable" ocular adnexal IgG4-related diseases and 13 (43.3%) of the 30 patients were diagnosed as MALT lymphoma with IgG4-positive plasma cells. Six cases of 13 IgG4-positive MALT lymphoma group had contralateral chronic inflammatory lesions infiltrated by IgG4-positive plasma cells, which was significantly (p = 0.007) higher than that in the IgG4-negative group. Conjunctival involvement was 69% of the IgG4-positive MALT lymphoma cases. Bilateral involvement of the ocular adnexa was significantly (p = 0.02) more frequent among IgG4-positive MALT lymphoma patients than that in IgG4-positive idiopathic orbital inflammation patients. Recurrence rate in the IgG4-positive group was higher (p = 0.05) than that in the IgG4-negative group but not significantly. Conclusions: This study presented an unusual framework of ocular adnexal IgG4-related inflammation, in conjunctiva. It is important to understand contralateral chronic inflammatory lesions and their relationship with IgG4-positive MALT lymphoma. Tissue biopsy and IgG4 immunostaining are required for all cases because IgG4-positive MALT lymphoma can arise from a pre-existing IgG4-positive chronic inflammatory lesions. This is the first study that performs IgG4 immunostaining for tissue from a relatively large number of conjunctival MALT lymphomas in a single center. Therefore, it will help to diagnose conjunctival lymphoproliferative disease.