Usefulness of Flow Cytometry in Diagnosis of IgG4-Related Ophthalmic Disease and Extranodal Marginal Zone B-Cell Lymphoma of the Ocular Adnexa

Although flow cytometry (FCM) is used to evaluate cell surface markers of various leucocyte populations quantitatively, little is known about the usefulness of FCM in lymphoproliferative disorders of the ocular adnexa. The aim of this study was to disclose results of FCM, which were compared among IgG4-related ophthalmic disease (IgG4-ROD), idiopathic orbital inflammation (IOI), and extranodal marginal zone B-cell lymphoma (EMZL).This is a retrospective observational study. Sixty-nine tumors comprising of 16 IgG4-ROD, 24 IOI, and 29 EMZL were enrolled in the study. All tumors, surgically excised, were diagnosed based on histopathology, immunoglobulin (Ig) heavy chain gene rearrangement, and FCM. In FCM, the percentage of T-cell markers (CD2, CD3, CD4, CD5, CD7, CD8), B-cell markers (CD10, CD19, CD20, CD23), NK cell marker (CD56) and cell surface kappa/lambda was searched based on medical records. Ig light chain restriction was evaluated from results in kappa/lambda deviation by FCM.The percentage of CD2, CD3, CD4, CD7, and CD10 was significantly higher in IgG4-ROD/IOI than EMZL (p<0.05 in every factor). In contrast, CD19 and CD20 percentages were significantly greater in EMZL than IgG4-ROD/IOI (p<0.01). There was no significant difference in any marker between IgG4-ROD and IOI. Kappa-positive cells were significantly greater in EMZL than IgG4-ROD/IOI (p<0.05). In kappa/lambda deviation, false-positive was noted in 3 (7.5%) benign IgG4-ROD/IOI and false-negative was observed in 10 (34.5%) EMZL cases. Sensitivity and specificity of Ig light chain restriction were 65.5 and 92.5%, respectively.Analyses of cell surface markers using FCM were useful in differentiating EMZL from IgG4-ROD/IOI. Sensitivity of Ig light chain restriction was relatively low in diagnosis of EMZL using FCM.