The natural history of cervical intraepithelial neoplasia as determined by cytology and colposcopic biopsy.

The smears preceding the histologic diagnosis of cervical intraepithelial neoplasia (CIN 3) were examined in 100 consecutive cases from an intensively screened population. In 60 patients, negative cytology has been recorded prior to the development of dysplasia; in 27 this had occurred within two years of the histologic diagnosis. These findings suggest that the transition time from epithelial normality to CIN 3 may be shorter than has been generally assumed; therefore, the intensity and frequency of screening should be reviewed.