Abstract
Oral fibrous hyperplasias (OFH) are thought to result from hyperplasia of collagen fibers. However, details regarding the presence of elastic fibers and reticular fibers other than collagen fibers in OFH are unclear. Therefore, this study focused on elastic fibers in the connective tissue with regard to OFH, and assessed the histopathological, histochemical, and immunohistochemical distribution of the elastic fibers.All cases of OFH (120 cases) were performed Elastica van Gieson (EvG) staining, and the distribution of elastic fibers was assessed using image analysis (binarization). Cases were classified into 2 groups; one group with elastic fibers (EF+ group) and one group without elastic fibers (EF−group).Elastic fibers were observed in 20 cases of fibroma of the buccal mucosa, 20 cases of fibroma of the labial mucosa, 19 cases of fibroma of the dorsal surface of tongue, 8 cases of fibroma of the gingiva, 1 case of fibrous epulis, and 1 case of fibromatous epulis. Histopathologically, elastic fibers were observed with mingled hyperplastic collagen fiber bundles and extended in the lesion. The distribution quantity of elastic fibers was fibroma of labial mucosa and buccal mucosa, and there were fewer elastic fibers in fibrous epulis and fibromatous epulis. Immunohistochemically, spindle cells in all cases of OFH were diffusely positive for Vimentin and negative for Actin, and CD34-positive spindle cells were interspersed into the connective tissue in EF+ group.In conclusion, elastic fibers were observed in 57.5% of OFH cases. The distribution of these fibers was site-specific, and differed from the collagen fibers that constituted OFH. CD34 positivity was observed in the spindle cells constituting OFH accompanied by elastic fibers, and undifferentiated mesenchymal cells around myogenic blood vessels near the lesion were related to the formation of a part of elastic fibers that constituted OFH.
