Quantitative detection of molecular markers ProEx C (minichromosome maintenance protein 2 and topoisomerase IIa) and MIB-1 in liquid-based cervical squamous cell cytology.

BACKGROUND

In this study, the authors conducted a comparative quantitative evaluation of the proliferation markers ProEx C (an aberrant S-phase induction marker, human papillomavirus E6-E7 correlated) and MIB-1 in squamous intraepithelial lesions (SIL) to identify a biomolecular profile informative for the diagnosis of high-grade SIL/cervical intraepithelial neoplasia 3 or greater that was complementary to the morphologic Papanicolaou (Pap) test ("biomolecular Pap test").

METHODS

After the cytologic diagnosis, reflex immunocytochemistry was carried out on 76 unstained SurePath cell samples (20 routine samples that were negative for intraepithelial lesion or malignancy and 56 positive samples that were selected with matching histology). Both a morphometric analysis with a software imaging analysis system and a quantitative analysis of atypical squamous clusters were performed.

RESULTS

The quantitative evaluation revealed an excellent, direct correlation between the 2 markers, although ProEx C was more selective and more informative for the progression of low- and moderate-grade lesions, because it only revealed cells in aberrant S-phase cell cycle. The quantitative morphometric analysis revealed the increased presence of atypical, positive clusters and the percentage of positive cells within, both paralleling the severity of the lesions. The threshold of a 3% ProEx C-positive nuclear area was useful for splitting lesions into groups with a low risk or high risk of progression.

CONCLUSIONS

Both ProEx C and MIB-1 were valid proliferation markers in cytologic preparations, and nuclear positivity was quantified successfully by using computer-assisted analysis. The analysis of atypical clusters may be a valuable tool in the diagnosis of SIL. The presence of atypical clusters and their positivity for proliferation markers are good first-glance indicators of lesion grade.