Objective: Conventional Pap smears exhibiting unequivocal features of ‘low grade squamous intraepithelial lesion' (LSIL) are occasionally mixed with some cells suspicious for, but not diagnostic of ‘high grade squamous intraepithelial lesion' (HSIL) on daily routine. The 2001 Bethesda System does not address the significance of such cytological entities. We have referred to these changes in our laboratory as ‘LSIL, atypical squamous cells cannot exclude HSIL' (LSIL/ASC-H). In this study, we aimed to compare the cytology and biopsy results of LSIL/ ASC-H to LSIL, ASC-H and HSIL.

Material and Method: Out of 37884 cases which were evaluated between 2005-2009 in our laboratory, cases interpreted as LSIL, LSIL/ ASC-H, HSIL and ASC-H were reevaluated and 153 cases for which biopsy materials were available were selected.

Results: The rate of histological CIN2 or worse associated with LSIL/ ASC-H (45%) was between the rates of LSIL (10%) and HSIL (65%), but not significantly different from ASC-H (50%). However, LSIL/ ASC-H was more frequently associated with a definitive histological diagnosis of any CIN2 than ASC-H (30% vs. 8%).

Conclusion: Based on our results, we recommend LSIL/ASC-H to be added to Bethesda System, and Pap test cases of LSIL/ASC-H may need to be clinically followed-up in a manner similar to ASC-H, i.e., with colposcopy for all patients.