Biomarker (ProExTM C, p16INK4A, and MiB-1) distinction of high-grade squamous intraepithelial lesion from its mimics

Topoisomerase II α and minichromosome maintenance protein 2 are proteins associated with aberrant S-phase induction. The current study evaluated the performance of these biomarkers (ProEx™ C; TriPath Oncology, Burlington, NC) compared with p16 INK4A and MiB-1 in distinguishing high-grade squamous intraepithelial lesions (HSILs) from HSIL mimics. We collected archival cervical biopsy, cone, and curettage specimens from 96 cases in which the differential diagnosis of HSIL vs reactive epithelial changes was considered. Hematoxylin- and eosin-stained slides were reviewed independently by three pathologists and scored for the presence or absence of SIL. Immunostains for ProEx C, p16, and MiB-1 were available for 95, 96, and 59 samples, respectively, and classified blinded to histological interpretation. Strong nuclear and cytoplasmic staining for p16 and staining for MiB-1 and ProEx C that extended beyond the lower one-third of the epithelium were scored as positive. χ 2 -tests and receiver operating characteristic analysis were conducted to statistically compare biomarker immunostaining performance against majority histological interpretation of SIL. Agreement between pathologists was also assessed by the κ -statistic. Inter-observer agreement ranged from fair to moderate ( κ =0.37–0.57). All three biomarkers correlated strongly with the majority diagnosis of SIL ( P