Both dermatopathic lymphadenopathy (DL) and immunoglobulin G4-related disease (IgG4-RD) are frequently complicated with allergic diseases. However, the relationship between DL and IgG4-RD is not well known. To clarify this relationship on the basis of clinical and pathological findings, including IgG4-positive (IgG4+) plasma cell infiltration in lymph nodes (LNs) of DL patients, we analyzed LNs of 11 DL patients using immunostaining of IgG, IgG4, forkhead box P3 (FOXP3), transforming growth factor (TGF)-β, interferon (IFN)-γ, and matrix metalloproteinase (MMP)-1, MMP-8, and MMP-13. Toluidine blue staining was also performed to identify mast cells. Of 3 patients with a high ratio of IgG4+/IgG+ cells (>40%) and elevated serum IgG4 levels, 2 developed IgG4-RD, whereas the other patient did not. Of 8 patients with a low ratio of IgG4+/IgG+ cells (<40%) or no infiltration of IgG4+ cells, 5 who could be followed did not develop IgG4-RD. The numbers of mast cells were similar to those of TGF-β-positive cells, and serial sections showed that mast cells possibly produce TGF-β. LNs of DL patients with a high ratio of IgG4+/IgG+ cells had significantly more mast cells and TGF-β-positive cells than those of patients with a low ratio of IgG4+/IgG+ cells or no infiltration of IgG4+ cells. However, no fibrosis was observed in LNs of both groups. IFN-γ was positive in interdigitating dendritic cells, Langerhans cells, and macrophages. MMP-1, MMP-8, or MMP-13 was expressed in macrophages. The lack of fibrosis in LNs may have been due to the production of IFN-γ, MMP-1, MMP-8, or MMP-13. Thus, DL with increased IgG4+ cells seems to be a phenotype of IgG4-RD in LNs.