The significance of endocervical cells and metaplastic squamous cells in liquid-based cervical cytology

We conducted a retrospective study to investigate whether the presence or absence of endocervical cells (EC) and metaplastic squamous cells (MSC) was associated with the detection of squamous intraepithelial lesions in liquid-based cervical cytology. 90,376 cases of liquid-based cervical cytology smears received in 2006 were included in the study. Low-grade (LSIL) and high-grade squamous intraepithelial lesions (HSIL) were classified according to the Bethesda system (2001). The rates of detecting LSIL and HSIL in smears with and without EC and/or MSC were determined. There were 1,540 LSIL and 396 HSIL. The ratio of HSIL/NILM (no intraepithelial lesion or malignancy) was 0.0022 in smears without EC or MSC, 0.0040 in smears with EC only, 0.0044 in smears with MSC only, and 0.0056 in smears with both EC and MSC present. Compared with smears without EC or MSC, this ratio was significantly higher (P < 0.05) when either EC or MSC was present. Compared with smears with EC only, the ratio was also significantly higher when both EC and MSC were present (P < 0.05). On the other hand, the presence or absence of EC had no effect on the detection rate of LSIL (0.0191 for both groups), while the presence of MSC was actually associated with lower detection rate of LSIL (0.0153, P < 0.05). The presence of endocervical and metaplastic cells was associated with higher detection rates of HSIL. MSC was associated with lower detection or LSIL.