Atypical squamous cells and low-grade squamous intraepithelial lesion in cervical cytology: cytohistological correlation and implication for management in a low-resource setting

Abstract

Objectives: To perform an audit of all cervical smears reported as atypical squamous cells (ASC) and low-grade squamous intraepithelial lesion (LSIL) as in the Bethesda system (TBS) 2001, and determine their histological follow-up and outcome when available, in order to define the threshold for colposcopic referral.

Material and methods: A total of 25,203 cervical smears were screened over a period of 3 years (January 2006 - December 2008) and all ASC and LSIL smears were reviewed with the corresponding histological follow-up. All cervical intraepithelial neoplasia (CIN) grade 2 lesions and above (CIN2+) were considered as clinically significant lesions for analysis.

Results: Out of 25,203 cervical smears, 424 (1.7%) were reported as ASC and 113 (0.4%) as LSIL. Additionally, three were reported as atypical cells, not otherwise specified. The ASC : SIL ratio was 2.18 : 1. Follow-up histology was available in 153 (36.8%) of the ASC cases and revealed CIN2+ lesions in 22 (14.4%). Follow-up histology was available in 50 (44.2%) of LSIL cases and revealed clinically significant abnormalities in five (10%), all of which were CIN2. CIN3 and invasive squamous carcinomas were seen in 5.9% and 1.4%, respectively, of cases of ASC, and not seen in LSIL. Reclassification of ASC smears into ASC-US (ASC-undetermined significance) and ASC-H (ASC- high grade SIL not excluded) revealed ASC-H in 2.6% of all ASC smears, with a clinically significant outcome in 45.4%.

Conclusion: In a low-resource setting where human papillomavirus testing is unaffordable, the threshold for colposcopic referral and follow-up histology should be ASC rather than SIL.