Purpose: Chronic inflammatory gingival lesions occur as pyogenic granulomas or non-specific chronic suppurative lesions. Methods: Of the 59 chronic inflammatory gingival lesions examined, plasma cell granuloma (n=14), which showed an intense antibody-mediated immune reaction with the increased infiltration of plasma cells, was observed as a pseudotumor-like gingival overgrowth and myofibroblastic or fibrohistiocytitc proliferation of stromal cells with a heavy collection of plasma cells. The levels of CD3, CD20, CD31, CD68, RANKL, cathepsin G, cathepsin K, lysozyme, TNFα, MMP-2, and MMP-9 in the 14 cases of gingival plasma cell granuloma with immunohistochemical detection were measured to determine the pathogenetic progresses of the plasma cell granuloma compared to the common pyogenic granuloma (n=45) in the gingiva. Results: The gingival lesions of the plasma cell granuloma could be divided into three histological types, plasma cell predominant type (PPT, n=8), mixed inflammatory cell type (MICT, n=2), and sclerosed fibrosis type (SFT, n=4). The PPT showed a condensed infiltration of plasma cells into the perivascular spaces of the granulomatous lesion with frequent formation of Russel`s body in their cytoplasm. The MICT showed the concomitant infiltration of many macrophages together with plasma cells, resulting in the diffuse destruction of stromal fibrous tissue. The SFT showed granulomatous lesions replaced gradually by thick collagenous fibrous tissue, resembling an inflammatory pseudotumor. The SFT expressed strongly the lymphocytic markers, CD3 and CD20, and the macrophage/monocyte markers, CD31 and CD68, but showed reduced expression of common inflammatory markers, TNFα, cathepsin G, lysozyme, MMP-2, and MMP-9, as well as the reduced expression of osteoclastogenic markers, RANKL and cathepsin K. Conclusion: These results suggest that a gingival plasma cell granuloma shows variable gene expression for cell-mediated immunity and stromal tissue degeneration, undergoing sclerotic fibrosis with a persistent inflammatory reaction.