Evaluation of atypical squamous cells on conventional cytology smears: An experience from a screening program practiced in limited resource settings

Background: The Bethesda system (TBS) 2001 has subdivided the category of atypical squamous cells (ASC) into: ASC-US (undetermined significance) and ASC-H (cannot exclude high-grade squamous intraepithelial lesion (HSIL)). The present study is an analysis of ASC-US and ASC-H cases diagnosed in a screening program practiced in limited resource settings. Methods: During the period January 2005 to December 2008, a total of 9190 smears were received, of which 568 were unsatisfactory. Cases initially diagnosed as ASC-US (n=74) and ASC-H (n=29) on conventional cytology smears were reviewed. Biopsy and human papilloma virus (HPV) results were available in limited cases. Results: On review, diagnosis of ASC-US was retained in 49 (66.2%) of the 74 initially diagnosed ASC-US cases. Remaining 12 cases were re-labeled as negative for intraepithelial lesion or malignancy (NILM), nine as low-grade squamous intraepithelial lesion (LSIL), three as ASC-H and one case as squamous carcinoma (SCC). Similarly, on review, diagnosis of ASC-H cases was retained in 17 of the 29 initially diagnosed ASC-H cases. Seven cases were re-labeled as NILM, three as HSIL and one case each as ASC-US and SCC. Overall, 8622 cases (96.6%) were diagnosed as NILM, 72 (0.83%) as LSIL, 121 (1.40%) as HSIL, 23 (0.26%) as SCC, 50 (0.57%) as ASC-US cases, 20 (0.23%) as ASC-H, five (0.05%) as atypical glandular cells (AGC) and two cases as adenocarcinomas. Out of 50 ASC-US cases, biopsy in 23 cases showed presence of CIN 1 in 16 cases (69.5%) and CIN 2 in one case (4.34%), while the remaining six cases were negative for CIN/malignancy. The remaining 20 cases with unavailable biopsy results were HPV-positive. Out of 20 ASC-H cases, biopsy in 15 revealed CIN 2 and above in 11 cases (73.3%). Three cases (20%) revealed CIN 1. Conclusions: Critical review is helpful in further reducing the number of ASC cases. The percentage of cases with CIN 2 and above is higher with ASC-H cases. The reason for relative increase in HSILs in the present study included referral bias in the screening program.