High prevalence of high grade squamous intraepithelial lesions and microinvasive carcinoma in women with a cytologic diagnosis of low grade squamous intraepithelial lesions.

Objective: To evaluate the histologic nature of low grade intraepithelial lesion (LSIL) in a region with a high prevalence of invasive cervical carcinoma and to propose a management protocol.
Study Design: Comparing the follow-up of 877 women with LSIL during a 43-month period, taking into consideration the histologic nature determined by colposcopic biopsy, endocervical curettage, conization or hysterectomy as the final pathologic diagnosis.
Results: During the study period, from July 1994 to February 1998, a total of 128,925 Pap smears were performed at our institute, with 877 (0.68%) diagnosed as LSIL. Among these, 722 women with CIN1-SIL and 32 with human papillomavirus-related changes (HPV-SIL) were enrolled in the study. Of the 543 women with CIN 1/squamous intraepithelial lesion, 145 (27%) cases of high grade squamous intraepithelial lesion were disclosed histologically, as were 16 (3%) cases of microinvasion. Among those followed at an interval of three months with a Pap smear alone, the persistence rate was 46.8%, while the regression rate was 40%. Thirty-two women with HPV/SIL underwent histologic evaluation, revealing 18% CIN 2/3 with no microinvasion.
Conclusion: A high percentage of CIN 2/3 as well as microinvasive lesions will go unnoticed in the absence of colposcopic evaluation.