In situ DNA hybridization analysis of human papillomavirus (HPV) sequences in benign oral mucosal lesions

Abstract

A series of 144 surgically treated benign oral mucosal lesions were analysed using an in situ DNA hybridization technique with ³⁵S-labeled human papillomavirus (HPV) DNA probes to demonstrate the DNA of HPV types 6, 11, 13, and 16, in routinely processed, paraffin-embedded biopsy specimens. These lesions and an additional 62 benign oral mucosal biopsy specimens (total, 206 specimens) were also assessed by the indirect immunoperoxidase (IP-PAP) technique to detect the expression of HPV structural proteins (viral antigens). A total of 54/206 (26.2%) lesions were observed to express HPV antigens, being found in 45/92 (48.9%) of the squamous cell papillomas/condylomas, in 1/54 fibrous hyperplasias, in 1/8 true fibromas, and in 7/8 (87.5%) of the focal epithelial hyperplasia (FEH) lesions. Of the HPV DNA-positive lesions, 15/45 (33.3%) expressed HPV antigens, the expression not being related to any particular HPV type. HPV DNA sequences were found in 45/144 (31.3%) of the lesions. HPV DNA was present with the highest frequency in FEH (83.3%), papillary hyperplasia (28.6%), fibrous hyperplasia (24.4%), and true fibromas (14.3%). The most frequent HPV type was HPV 11, representing 37.8% of the DNA-positive lesions. HPV 13 DNA, previously regarded as specific to FEH, was disclosed as a single HPV type in seven cases, and as a double infection by HPV 11 and 13 in an additional three cases, including all five morphologically distinct entities. Noteworthy is the discovery, of the high-risk HPV type 16 DNA in 17.8% of the DNA-positive lesions, four papilloma/condyloma lesions, three fibrous hyperplasias, and one FEH. The results confirm the previously reported evidence regarding HPV involvement in oral mucosal lesions. The implications of these findings are discussed in terms of the epidemiology, HPV etiology, and proper classification of the oral mucosal lesions, with special emphasis on the discovery of the high-risk HPV type 16 in the benign lesions as well as in oral cancer. The use of the in situ DNA hybridization as a powerful tool in detecting the specific HPV DNA sequences in routinely processed oral biopsy specimens is strongly recommended.