p16/Ki‐67 dual‐stain cytology in the triage of ASCUS and LSIL Papanicolaou cytology

Abstract

Most human papillomavirus (HPV) infections are transient. 1 Among other things, unnecessary overtreatment can cause unnecessary future pregnancy complications, but an approach to persistent HPV infection that is too cavalier may result in unacceptably high rates of cervical carcinoma. 2 Cytologists recognize some of the morphologic changes in Papanicolaou (Pap) tests with an excellent specificity, but a single test is associated with a low sensitivity (70%). Screening specificity is greatly improved by the addition of HPV testing for triage of mildly abnormal Pap smears (atypical squamous cells), and sensitivity is increased through co-testing for primary screening. Improved sensitivity, though, is almost always hampered by decreased specificity. It is really hard to drive both sensitivity and specificity. Being able to improve either or both cervical management strategies would have an impact on narrowing and improving the referral population of patients for colposcopic examination. This improvement may be here in the form of dual immunohistochemical staining for p16 and Ki67 in cervical cytology samples, as discussed in the article by Schmidt et al. in the current issue of Cancer Cytopathology. 1 To appreciate their article, a few pathways need to be understood at a basic level. CINtecþ is the product name by the German-based company mtm (mtm laboratories AG, Heidelberg, Germany) of the dual-stain immunohistochemical kit for p16 and Ki67. It is a relatively simple biomarker that capitalizes on the disruption of the retinoblastoma protein pathway. E2F is a transcription factor that helps commit a cell to divide but is inactive when bound to retinoblastoma protein (Rb). When the E7 portion of high-risk HPVs binds to the host epithelial cell Rb, then E2F is released. This results in committing a cell to divide (Therefore, in tissue samples, we see an increase in suprabasal dividing cells, which can be detected by the use of cell cycle antibodies such as Ki67.) and simultaneously the negative regulator p16 attempts to slow down and balance cell cycling because it, too, is activated by free E2F. In uninfected squamous epithelium, p16 is normally only rarely detectable by immunohistochemistry in the basal cells. In contrast, there is a paradoxical increase in p16 in high-grade dysplasia, which can also be detected with immunohistochemistry.

Combining HPV DNA load with p16/Ki-67 staining to detect cervical precancerous lesions and predict the progression of CIN1–2 lesions

“…It was interesting to note that the combination of all 13 HPV loads showed no improvement in either the sensitivity or specificity of the p16/Ki-67 test for the prediction of CIN or more severe lesions. However, amongst those patients with HPV-16 and/or 58 infection, a combination of the HPV-16 and/or 58 DNA load with p16/Ki-67 staining increased the sensitivity of the detection of CIN1+ and CIN2+ lesions, though p16 and Ki-67 tests were proven to be a highly sensitive method to estimate CIN2+ cytological cases [9, 22, 23]. Whilst the combination of HPV-16 and/or 58 DNA loads achieved only a modest improvement in the detection of CIN3+, the elevated expression of p16/Ki-67 closely correlated with severe neoplastic lesions or more severe HPV positive cases [9, 23, 24].…”

Usefulness of CINtec® PLUS p16INK4a/Ki-67 Double-Staining in Cytological Screening of Cervical Cancer

“…Use of these potential predictors should be seriously considered in the management of patients with equivocal cytology. Schmidt et al [49,50] reported that p16/Ki-67 dual-stain cytology showed high sensitivity and specificity for the detection of underlying CIN2+ in women with ASCUS and LSIL in Pap cytology. Furthermore, Petry et al [51] reported that p16/Ki-67 dual-stained cytology may help identify underlying high-grade disease in Pap-negative HPV-positive women.…”

Immunohistochemical Expression of Cyclin D1, p16Ink4a, p21WAF1, and Ki-67 Correlates With the Severity of Cervical Neoplasia

“…Immunostaining of p16 has proved to be especially useful for distinguishing CIN from regenerative atypias, immature metaplasia, and atrophic epithelium (43,44), contributing to a significant increase in the accuracy and reproducibility of the diagnosis (16)(17)(18)20,37,40). Some studies have showed that p16-positive expression is a potential predictor of both progression of the low-grade lesions (19,37) and survival outcome after chemoradiation therapy for advanced-stage invasive cervical carcinoma (45).…”