A rare case report on IgG4-positive orbital B-cell non-Hodgkin lymphoma

IgG4-related disease (IgG4-RD) is a chronic autoimmune condition characterized by fibrosis and inflammation affecting multiple organs. The association between IgG4-RD and an increased risk of lymphoma remains debated. A 68-year-old man presented with painless, gradually enlarging swelling in the left orbit over the past 7 months. His thyroid function tests were normal. The serum IgG4 level was found to be very high (874 mg/dL). Histopathological and immunohistochemical analysis of the left orbital tissue suggested IgG4-positive orbital B-cell non-Hodgkin lymphoma. Immunohistochemistry showed positive staining for CD20, CD3, and Ki-67, along with lambda light chain restriction. More than 50% of the plasma cells stained positive for IgG4. Patients with IgG4-RD have a higher risk of developing lymphoma compared to the general population, highlighting the importance of screening for non-Hodgkin lymphoma during diagnosis and treatment of IgG4-RD.