Human papillomavirus type 13 and focal epithelial hyperplasia of the oral mucosa: DNA hybridization on paraffin-embedded specimens.

16 cases of focal epithelial hyperplasia (Heck's disease) were studied for the presence of human papillomavirus DNA by means of nucleic acid hybridization. Hybridization was carried out in situ with biotin-labelled probes of HPV 1, 6, 11, 13, 16, and 18 DNA under stringent and non-stringent conditions. Under non-stringent conditions, 6 of 16 cases (38%) hybridized to a mixture of HPV 1, 6, 11, 16, and 18 DNA. When these probes were applied under stringent conditions, only one case could be shown to be weakly positive for HPV 6/11 DNA. Further stringent hybridizations, which were conducted with a HPV 13 probe on 12 of our 16 cases, revealed a positive result in 9 of 12 cases (75%). The results of our study strongly substantiate the concept that HPV 13 or a closely related HPV type is associated with lesions morphologically presenting as focal epithelial hyperplasia.