Reassessment of the morphological continuum of cervical intraepithelial lesions: does it reflect different stages in the progression to cervical carcinoma?

Currently used histological and cytological classification systems for cervical lesions are reviewed. These suffer from poor inter- and intra-observer reproducibility, and do not allow accurate identification of which mild lesions will progress towards cancer. The Bethesda classification system is described and it is postulated that low-grade and high-grade squamous intraepithelial lesions might represent distinct entities with different potential for progression rather than necessary stages of a continuum leading to cervical cancer. Improved understanding of the etiological role of HPV types in cervical cancer and of the natural history of low- and high-grade intraepithelial lesions might result in more suitable clinical treatment of low-grade lesions.