Abstract
The 1988 Bethesda System for reporting cervical and vaginal cytologic diagnoses dramatically altered the diagnostic categories at the lower end of the cytologic spectrum. The primary impetus for this change was the diagnostic variability and clinical confusion inherent in the class 2 Papanicolaou (Pap) group, which included a spectrum of cellular changes that ranged from normal to definitive manifestations of human papillomavirus (HPV). If clinical confusion were to be diminished, it was clearly necessary to clarify the nature of each class 2 cellular change more specifically. Unfortunately, some atypia remained ambiguous and were designated atypical squamous cells of undetermined significance (ASCUS). The designation "undetermined" highlights the continuing dilemma regarding cells that have no distinguishing characteristics to further clarify their nature. The category has been a major clinical issue, with 2 to 3 million women given a diagnosis that generates uncertainty each year.1,2 The magnitude of the concern is highlighted by a major commitment by the National Cancer Institute to evaluate the best triage option for women with equivocal and low-grade Pap smears in a randomized trial that began in 1995 and will end in 2001.3