Histopathological, Immunohistochemical and Exfoliative Cytological Studies of Oral Verruciform Xanthoma

Verruciform xanthoma is a rare tumor-like lesion, predominantly affecting the oral mucosa. Although several studies of verruciform xanthoma have been reported, the characteristic features and pathogenesis have not been fully clarified. The purpose of the present study is to perform immunohistochemical analysis using markers of proliferative cell activity and cytokeratins, and to perform comparative analysis between cytological and histological features in order to clarify the characteristic features of verruciform xanthomas. Histological findings showed exophitic proliferation of stratified squamous epithelium and accumulation of foamy macrophages between epithelial processes. Immunohistochemically, accumulated foamy cells showed positive immunoreactivity for CD68, and positive cells were also present in the epithelium. Expression of pan-cytokeratin was observed in most layers of the epithelium, whereas cytokeratin 13 was also detected in prickle cell layers. Positive reactivity for Ki-67 was observed in epithelial cell nuclei. Positive reactivity was largely distributed in basal and/or parabasal cell layers, and the positive cell rate was 20%. In addition, exfoliative cytological findings showed hyperkeratotic epithelial cells with picnosis, thus suggesting the characteristics of hyperplastic epithelium in verruciforma, although foamy cells were not observed in the cytological specimens. These results suggest that benign morphological characteristics with local cellular immune response of verruciform xanthoma may be evaluated based on immunohistochemical expression of cytokeratin and Ki-67, as well as exfoliative cytological findings.