Is the Expression Pattern of BD ProEx C the Same as Ki67? A Comparative Analysis in Cervical Intraepithelial Lesions (CIN)
S Bose, A Walts. Cedars Sinai Medical Center, Los Angeles, CA
Background: BD ProEx C (ProExC) is a reliable marker for high grade CIN that can be applied to tissue sections to confirm the diagnosis of high grade (HG) CIN and to triage cases of atypical squamous metaplasia. ProExC is a novel immunohistochemical assay that combines two antibodies directed against topoisomerase IIa and minichromosome maintenance protein 2, both of which play important roles in DNA replication during S phase. Ki67, another cell proliferation indicator expressed during all phases of the cell cycle except G0 has also been demonstrated to be aberrantly expressed in HG CIN lesions and is also used as a biomarker for HG CIN. This study was designed to determine if the expression patterns of ProExC and Ki67 are similar.
Design: 158 cases of CIN including 39 benign/reactive, 21 atypical squamous metaplasia (ASQM), 47 low grade CIN, and 51 HG CIN cases were retrieved from our files. All cases had p16, ki67 and ProExC immunostains. Women in the study ranged in age from 19 to 83 years (mean: 36 yrs; median 32 yrs). HE and immunostained slides were evaluated by two pathologists and consensus diagnoses were recorded. Percent of positively stained nuclei were recorded as 0-25, 25-50, 50-75 and 75-100%. Cases with discrepant results were analyzed.
Results: 54 (34%) cases showed discrepant results, the majority (46 cases, 29%) showing a one-step discordance whereas a minority (8 cases, 5%) showed a difference of two steps or more. One-step discordant staining was noted across all morphologic diagnoses (varying between 23-39% of cases in each of the diagnostic categories). Two-step discordant staining was noted most frequently in cases with ASQM (3 cases, 14%). A minority of LG (3 cases, 6%) and HG CIN (2 cases, 4%) also showed this difference. Using >50% positive staining as a cut-off for a positive result, 14 (9%)discordant cases were noted, of which 7 were positive with ProExC (4 of which were strongly positive for p16) and 7 were positive with Ki67, of which 4 were strongly positive for p16.
Conclusions: Although both ProEx C and Ki67 are markers of aberrant proliferation, expression patterns are different in 34% of CIN with significant differences in a minority (5%).
Monday, March 9, 2009 1:00 PM
Poster Session II # 135, Monday Afternoon