Aims: Orbital inflammatory pseudotumor is considered a non-neoplastic inflammatory process. The finding of clonality of B or T-cell receptors in cases pathologically diagnosed as orbital inflammatory pseudotumor has unknown clinicopathologic significance. We sought to investigate potential B and T-cell clonality and concomitant diseases in cases pathologically diagnosed as orbital inflammatory pseudotumor.
Methods: Cases diagnosed as orbital inflammatory pseudotumor at our institution were retrospectively analyzed. Hematoxylin and eosinstained slides, immunohistochemically stained slides and polymerase chain reactions on cell block material for the investigation of clonality of B and T-cell receptors were evaluated, to confirm the diagnosis and investigate the prevalence of concomitant diseases.
Results: A total of 13 cases showing characteristic histopathologic features of orbital inflammatory pseudotumor were identified. CD138, IgG, and IgG4 showed varying numbers of plasma cells in each case, with 5 cases (5/13, 38%) exhibiting relative increase in the presence of IgG4 plasma cells. However, no cases showed diagnostic findings of IgG4-related disease (IgG4-RD). polymerase chain reactions analysis showed clonal B-cell populations in 2 cases (2/13, 15%). No cases showed anaplastic lymphoma kinase expression by immunohistochemistry. There were no clinical reports of progression to lymphoma or development of systemic IgG4-RD in any of the patients (average follow-up of 300 days), with 38% of patients showing systemic autoimmune conditions.
Conclusion: A small but significant percentage of typical orbital inflammatory pseudotumor on histology showed B-cell clonality on polymerase chain reactions analysis of B-cell receptors, or features suggestive, but not diagnostic of IgG4-RD. Close follow-up of these patients to identify development of lymphoma, systemic IgG4-RD, or other rheumatologic conditions may be clinically warranted.