Cytological features of ASC-US in The Bethesda System 2001

—Comparative analysis between smears processed by the conventional Papanicolaou method and the liquid-based ThinPrep method—

Abstract

Objective : To clarify the cytological features of atypical squamous cells of undetermined significance (ASC-US) of the cervix, which are still not popular among cytotechnologists and cytopathologists in Japan.
Study Design : A total of 11,039 cervical samples enrolled from multiple hospitals in Japan were analyzed using split-sample processing by the conventional Papanicolaou (CP) and liquid-based ThinPrep (TP) methods. The cytological features of ASC-US were highlighted to compare the histological diagnoses, and all positive samples were examined for the prevalence of HPV by the Multiplex PCR method.
Results : ASC-US was detected more frequently (p<0.0001) in the CP smears at the rate of 1.8% than in the TP smears at the rate of 1.1%. High grade squamous intraepithelial lesions or more advanced were detected more frequently (p<0.001) in the TP smears at the rate of 5.1% than in CP smears at the ratio of 4.1%. In regards to the cytological features of ASC-US in the CP smears, characteristic qualitative insufficiency of nuclear atypism was found due to dehydration or degeneration. Conversely, the TP smears showed an increased nuclear/cytoplasmic ratio with slightly increased chromatin.
Conclusions : For correct diagnosis of ASC-US, its definition and the differences in the features observed between smears processed by different methods must be understood clearly.