Human papillomavirus-associated early vulvar neoplasia investigated by in situ hybridization.

Of 21 consecutive cases of early vulvar neoplasia studied at the Istituto Nazionale Tumori of Milan, 62% appeared to be related to papillomavirus infection. This conclusion is the result of the present study by in situ hybridization with DNA probes of human papillomavirus (HPV) 6/11, 16, and 18 and of previous ultrastructural and immunohistochemical investigations. The proportion of cases associated with HPV was 78.5% for those (11/14) with histologic evidence of viral infection and 33% for those without (2/6). HPV 16 was detected in all cases that were positive by in situ hybridization except for one, which showed HPV 6/11 DNA. In one case there was a mixed triple infection for HPV 6/11, 16, and 18. The patient who was positive for HPV 6/11 had a giant condyloma associated with an inguinal lymph node containing a metastatic well-differentiated squamous cell carcinoma. Three cases were positive for papillomavirus internal capsid species-nonspecific antigen (PV-Ag) (with ultrastructural evidence of virions in one of them) and were negative for HPV-DNA hybridization. They appeared to be infected with a type of HPV not identified by the available probes. Three cases, and two sites of two other cases with double infection, were HPV-DNA-positive and PV-Ag-negative. They illustrate the limitation of immunohistochemical investigation in cases with high-grade intraepithelial neoplasia. Six cases of verrucous carcinoma of the vulva were negative for HPV DNA by in situ hybridization.