A Histopathological and Immunohistochemical Study of Cell Proliferative Activity in Epulis Osteoplastica and Epulis Fibrosa

Abstract

Epulis, a relatively common benign polypoid lesion of the gingiva, may be pathologically classified into several subtypes. Although an epulis is thought to be reactive cell proliferation in the gingiva to various stimuli, the mechanism of pathogenesis is unclear. The present study examined histopathological and immunohistochemical analyses to elucidate the cell proliferation in epulis osteoplastica (n=8) using Ki-67 monoclonal antibody MIB-1 as a marker of proliferation and compared that to cell proliferation in epulis fibrosa (n=8). Epulis osteoplastica consisted of massive, trabecular, or woven bone formation surrounded by a proliferation of fibroblasts and blood vessels with minimal inflammatory cell infiltration under the mucosal squamous epithelium. Scanty osteoblastic lining was observed around the bone. Epulis fibrosa was composed of a proliferation of fibroblasts, collagen fibers, and blood vessels with minimal inflammatory cell infiltration ; no evidence of bone formation was found. Immunohistochemically, positive reactivities for MIB-1 were observed in the fibroblasts of epulis osteoplastica and epulis fibrosa, although positive cell rates were higher in epulis osteoplastica than in epulis fibrosa. The findings suggest that epulis osteoplastica has neoplasm-like characteristics unlike epulis fibrosa.