Immunohistochemical detection of filaggrin in preneoplastic and neoplastic lesions of the human oral mucosa.

The distribution pattern of filaggrin in lesions of human oral mucosa was studied with the use of an anti-filaggrin serum raised in rabbits. A peroxidase-antiperoxidase method for the detection of filaggrin was applied to specimens from 9 cases of leukoplakia, 5 cases of verrucous carcinomas, 2 cases of carcinoma in situ, and 5 cases of invasive carcinoma. Areas of normal mucosa with different stages of keratinization were available in the same biopsy specimens. The granular layer of normal orthokeratinized epithelium was positive, whereas the horny layer was negative. Parakeratinized and nonkeratinized epithelia stained less than orthokeratinized epithelium. In leukoplakia and verrucous carcinoma, the reaction was irregular both in the granular and the cornified layers. Carcinoma in situ had a virtually negative reaction, and invasive carcinoma exhibited a slight positive reaction in the more differentiated areas. The immunohistochemical demonstration of altered filaggrin patterns in oral lesions correlates well with the degree of epithelial dysplasia and could be a helpful tool in grading white lesions and neoplasms of the oral mucosa.