Comparison of IgG4-Related Lymphadenopathy and Multicentric Castleman's Disease: a Retrospective Study.

Background: It can be difficult to distinguish between IgG4-related lymphadenopathy and multicentric Castleman's disease (MCD) because these conditions cannot be differentially diagnosed using immunohistochemical staining alone. In this study, we analyzed the clinical features of IgG4-related lymphadenopathy and MCD patients.

Methods: We retrospectively analyzed 27 patients with MCD, including 20 with plasma cell-type (PC-type) and 7 with hyaline vascular (HV) features (mixed-type). An additional 15 patients with IgG4-related lymphadenopathy were enrolled. Clinical data and immune pathological characteristics, including serum interleukin-6 (IL-6) levels, lymph node lesion biopsies, IgG4+/IgG+ expression, and 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) images, were collected.

Results: The serum levels of C-reactive protein (CRP), IgA, and IL-6 were significantly elevated in the PC/mixedtype group compared with the IgG4-related lymphadenopathy group (p < 0.05). By contrast, the mean age, eosinophilia, globulin, and serum levels of IgG and IgG4 were significantly higher in the IgG4-RD lymphadenopathy group (all p < 0.05). Thirty percent of patients with IgG4-RD lymphadenopathy had elevated IL-6 levels, and 50% with MCD had elevated serum IgG4 levels. Immunohistochemical studies demonstrated the presence of numerous IgG4+ plasma cells, which accounted for > 40% of IgG4/IgG+ cells in 7 of 27 cases in the PC/mixed-type group. We first found that the mean maximum standard uptake value (SUVmax) was strongly associated with albumin and IL-6 in the IgG4-RD lymphadenopathy group, but not in the MCD group. The number of involved organs, but not the standard uptake value (SUV), helped to distinguish between the two diseases. Most PC/mixed-type group patients responded poorly to glucocorticoids when administered alone or in combination with immunosuppressant drugs.

Conclusions: MCD cannot be differentiated from IgG4-related lymphadenopathy using histology alone. Systematic comparative analysis; clinical and laboratory analyses, especially 18F-FDG-PET/CT; and responses to drug treatment are therefore important parameters for distinguishing between these two diseases.