Perifollicular granulomatous inflammation in reactive lymph nodes: a possible morphologic marker for IgG4 plasmacytosis

IgG4-related sclerosing disease is a steroid-responsive syndrome of possible autoimmune origin that can manifest with mass-like lesions in a variety of organ sites. Lymph node involvement may clinically mimic malignant lymphoma, Castleman disease, or infectious lymphadenitis; consequently, accurate diagnosis is necessary to exclude other processes and to initiate steroid therapy appropriately. Histologically, a number of relatively nonspecific features have been associated with IgG4-related lymphadenopathy, mainly increased plasma cells in an interfollicular or intra-germinal center pattern. We describe seven lymph node cases with distinctive perifollicular granulomas, in a concentric or crescent-like arrangement, partially or completely encircling lymphoid follicles. This finding was specifically associated with a marked intra-germinal center increase in IgG4-positive plasma cells, as compared to other patterns of nodal granulomas in a series of control cases. We discuss the clinicopathologic features of these cases, including an unusual presentation in a pediatric patient. This study adds to the morphologic spectrum of IgG4-related lymphadenopathy.