Human papillomavirus. International Academy of Cytology Task Force summary. Diagnostic Cytology Towards the 21st Century: An International Expert Conference and Tutorial.

ISSUES: Cervical squamous cell carcinomas, adenocarcinomas and their precursors are caused by the human papillomavirus (HPV). Although HPV appears to be essential to the transformation of these epithelial cells, it is not sufficient, and a variety of cofactors and molecular events must take place between when an HPV infection occurs and a cervical cancer or its precursor develops. This review examines the data supporting these contentions, briefly outlines the molecular events that occur, considers the epidemiology and natural history of the disease, and details the implications of using HPV detection and typing in both clinical management and population-based screening programs. CONSENSUS POSITION: 1. Based on the available molecular, clinical and epidemiologic data, a subset of HPVs are unequivocally the etiologic agents for cervical cancers and their precursors. 2. Different mucosotropic HPVs have varying neoplastic potential. However, the great majority of cervical HPVs have oncogenic potential. Since oncogenic HPV-induced epithelial transformation to a high grade lesion or cancer is rare relative to the rate of infection, the term high risk is discouraged. 3. HPV's interaction with host cells has two principal biologic consequences: a) All anogenital HPVs induce low grade squamous lesions, which are the morphologic correlate of a productive infection. b) Rarely, HPVs induce a proliferative epithelial phenotype that pathologists recognize as a high grade lesion and that is the proximate cytohistologic precursor of invasive cervical carcinoma. 4. HPV biology and issues of practical clinical management should be reflected in the classification systems used for cytologic and histologic diagnosis. ONGOING ISSUES: The molecular identification of HPVs (HPV testing) potentially may be very useful for primary screening or secondary triage of patients with certain lesions. However, the technology available to the practicing clinician is still evolving. Optimization of type spectrum, sensitivity, specificity and ease of use is under development. Data regarding these factors as well as a clear cost benefit analysis are sparse or pending in several large trials. Until such data are available, caution in clinical implementation of HPV testing is warranted.