The Bethesda system and evaluation of abnormal pap smears.

The Bethesda Pap Smear system and its 1991 revisions aim to simplify Papanicolaou (Pap) smear reporting and make it more reproducible. It redefines the Pap smear request as a medical consultation. The pathologist consultant is required not only to provide the smear reading but also its clinical recommendation. The Bethesda system insists on a detailed Pap smear report assessing specimen adequacy and types of epithelial changes. Squamous cell abnormalities are grouped according to their biologic potential. Both cervical intraepithelial neoplasia, grade I (CIN I) (mild dysplasia) and human papillomavirus (HPV) lesions are grouped together as low-grade squamous intraepithelial lesions (LGSIL), while moderate and severe dysplasia (CIN II and III) belong to the high-grade squamous intraepithelial lesion (HGSIL) category. Atypical squamous cells of undetermined significance (ASCUS) and atypical glandular cells of undetermined significance (AGCUS) need further qualification as to whether they favor either a reactive or neoplastic process. Guidelines for management of abnormal Pap smears are discussed in detail.