IMP3 is a novel biomarker for adenocarcinoma in situ of the uterine cervix: an immunohistochemical study in comparison with p16(INK4a) expression.

Adenocarcinoma in situ of the uterine cervix remains a diagnostic challenge in a small proportion of cases. This suggests a need for biomarker that may be of help in establishing the diagnosis. The aim of this study was to evaluate the potential of insulin-like growth factor-II mRNA-binding protein 3 and cyclin-dependent kinase inhibitor p16(INK4a) as biomarkers for adenocarcinoma in situ. Forty-four samples of adenocarcinoma in situ from 40 patients and 23 control cases of benign uterine cervix were included in this study. In addition to benign endocervical epithelium, 19 of these 23 control cases also showed focal tubal metaplasia. Cytoplasmic immunoreactivity for insulin-like growth factor-II mRNA-binding protein 3 was identified in 41 (93%) adenocarcinoma in situ samples, among which, 29 (71%), 10 (24%), and 2 (5%) samples showed insulin-like growth factor-II mRNA-binding protein 3 positive staining in 50% or more, >5 to <50 and <5% of adenocarcinoma in situ lesional cells, respectively. Immunohistochemical reaction intensity for insulin-like growth factor-II mRNA-binding protein 3 was found to be strong in 34 adenocarcinoma in situ samples, intermediate in five, and weak in two. All 23 control cases were negative for insulin-like growth factor-II mRNA-binding protein 3. p16(INK4a) expression was identified in all of the adenocarcinoma in situ samples with intermediate staining intensity seen in seven samples and strong in the remainder. Fourteen of 19 (74%) tubal metaplasia cases showed p16(INK4a) immunoreactivity in >50% of the tubal metaplastic epithelium with staining intensity ranging from weak to strong. Our findings demonstrate significant expression of insulin-like growth factor-II mRNA-binding protein 3 and p16(INK4a) in adenocarcinoma in situ as compared to benign endocervical glands, suggesting that expression of these biomarkers may be helpful in the distinction of adenocarcinoma in situ from benign endocervical glands, particularly in difficult borderline cases.