Utility of CK7 Versus p16 as a Prognostic Biomarker in CIN 2

Cervical intraepithelial neoplasia (CIN) 2 is an equivocal diagnosis, with p16 immunohistochemical positivity currently recommended for diagnostic confirmation. Biomarkers characteristic of squamocolumnar junction cells were recently found to be positive in almost all CIN 2 and CIN 3. CIN 1 lesions which express squamocolumnar junction markers (in particular cytokeratin 7 [CK7]) are associated with a higher rate of subsequent high-grade squamous intraepithelial lesion, suggesting that CK7 may be a useful prognostic biomarker for CIN 1. We sought to determine the utility of CK7 as a prognostic biomarker in the setting of morphologic CIN 2, and to compare this to the utility of p16 in this setting. We performed CK7 immunohistochemical on 116 cases originally diagnosed as CIN 2. Of these, 68.1% were p16 and 90.5% were CK7. A total of 19.5% of patients had a subsequent diagnosis of CIN 3 on biopsy or excision; the index CIN 2 lesion was CK7 in all of these cases (sensitivity 100%) and p16 in all but 1 (21/22; sensitivity 95.5%). The specificity of p16 (37.4%) and CK7 (8.0%) for predicting subsequent CIN 3 were significantly different (P<0.001). While p16 expression was significantly associated with subsequent CIN 3 (P=0.002), CK7 expression was not (P=0.202). We conclude that CK7, unlike p16, is not useful as a prognostic biomarker in CIN 2. While it is still promising as a prognostic marker in CIN 1, additional studies are needed to determine optimal staining/interpretation criteria.