The significance of squamous metaplasia in the development of low grade squamous intraepithelial lesions in young women.

BACKGROUND The purpose of this study was to examine, prospectively, the presence and extent of cervical epithelial immaturity as well as the rate of squamous metaplastic activity as a risk for the development of low grade squamous intraepithelial lesions (LSIL). METHODS The study was a nested case-control design that used subjects from an ongoing cohort study of human papillomavirus infection. Fifty-four sexually active young women who developed LSIL were matched for age and number of visits with 54 women who had never developed LSIL. The percent of cervical immaturity was interpreted from colpophotography using a computer-generated pixel count of delineated immature and total cervical areas. Activity of squamous metaplasia was interpreted as the percent change in the area of immaturity over a defined time period. Conditional logistic regression analysis examined risks for the development of LSIL. RESULTS Baseline area of biologic immaturity was not a predictor of LSIL. However, women with the a high degree of metaplastic activity near the SIL event were more likely to develop LSIL (odds ratio = 3.01 [95% confidence interval, 1.3, 6.8] for every 10% unit change in area of immaturity). CONCLUSIONS A rapid rate of metaplastic change within the transformation zone, rather than the initial area of biologic immaturity, is a significant risk factor for the development of LSIL. Cancer 1999;85:1139–44. © 1999 American Cancer Society.