Immunocytochemistry of p16INK4a in liquid-based cervicovaginal specimens with modified Papanicolaou counterstaining

Diagnostic performance of p16 staining in atypical squamous cells 'cannot exclude high-grade squamous epithelial lesion' in predicting high-grade cervical pathology

Atypical squamous cells 'cannot exclude high-grade squamous epithelial lesion' (ASC-H) cytology represents clear risk and has been a controversial issue in clinical practice. The objective of this study is to investigate the diagnostic performance of p16(INK4A) immunohistochemistry (IHC) among ASC-H Pap smears in predicting high-grade cervical intraepithelial lesions. Decolourisation and staining process with p16(INK4A) is applied to 27 ASC-H diagnosed conventional Pap smears, which were all managed with colposcopy-directed cervical biopsy priorly. Staining characteristics of ASC-H Pap smears were compared with histopathological data and sensitivity-specificity values of p16 triage to detect CIN2 + histopathology were determined. The sensitivity and specificity of positive p16(INK4A) immune staining to detect CIN2 + histopathology were as 87.5% and 68%, respectively. The positive predictive value of p16 triage is found as 53.8% and negative predictive value was as 92.8%. p16(INK4A) IHC seems applicable for conventional Pap smears and may provide an alternative triage option in ASC-H category.

p16(INK4a) immunostaining in cytological and histological specimens from the uterine cervix: a systematic review and meta-analysis

BACKGROUND

P16(INK4a) is a biomarker for transforming HPV infections that could act as an adjunct to current cytological and histological assessment of cervical smears and biopsies, allowing the identification of those women with ambiguous results that require referral to colposcopy and potentially treatment.

MATERIAL AND METHODS

We conducted a systematic review of all studies that evaluated the use of p16(INK4a) in cytological or histological specimens from the uterine cervix. We also estimated the mean proportion of samples that were positive for p16(INK4a) in cytology and histology, stratified by the grade of the lesion.

RESULTS

Sixty-one studies were included. The proportion of cervical smears overexpressing p16(INK4a) increased with the severity of cytological abnormality. Among normal smears, only 12% (95% CI: 7-17%) were positive for the biomarker compared to 45% of ASCUS and LSIL (95% CI: 35-54% and 37-57%, respectively) and 89% of HSIL smears (95% CI: 84-95%). Similarly, in histology only 2% of normal biopsies (95% CI: 0.4-30%) and 38% of CIN1 (95% CI: 23-53%) showed diffuse staining for p16(INK4a) compared to 68% of CIN2 (95% CI: 44-92%) and 82% of CIN3 (95% CI: 72-92%).

CONCLUSION

Although there is good evidence that p16(INK4a) immunostaining correlates with the severity of cytological/histological abnormalities, the reproducibility is limited due to insufficiently standardized interpretation of the immunostaining. Therefore, a consensus needs to be reached regarding the evaluation of p16(INK4a) staining and the biomarker needs to be assessed in various clinical settings addressing specific clinical questions.

Human papillomavirus mRNA and p16 detection as biomarkers for the improved diagnosis of cervical neoplasia

Human papillomavirus (HPV) infection of the genital tract is very common and normally follows a benign clinical course; however, in an unfortunate minority of infected individuals, it can cause disease that sometimes leads to cancer. It is accepted that HPV DNA testing has a role in the management of cervical disease both in a prevaccination and postvaccination era; however, to improve the specificity of this approach, there is a requirement to develop and validate tools/assays that can identify women at risk for progressive disease. There is evidence to suggest that detection of viral gene expression both directly and indirectly may constitute a more specific approach for delineating clinically significant infection compared with HPV DNA-based assays. HPV oncogene expression and evidence of its deregulation can be monitored through direct detection of viral mRNA transcripts or through detection of the cellular protein p16. For both approaches, commercial assays have been introduced and numerous studies have been conducted. The present article describes the scientific theory underpinning these approaches, their amenability to routine-diagnostic specimens/settings, and the clinical data that has been garnered through their application thus far. Currently, there is promising data indicating that HPV mRNA and p16 might play an important role in future cervical cancer screening scenarios. Still, large randomized studies are necessary to confirm the preliminary data.

METHODS

PubMed and OVID were interrogated with search terms "HPV RNA;" "HPV mRNA;" "HPV transcript-detection, testing, and methods;" "p16" AND "cervical cancer;" "p16" AND "CIN;" "p16" AND "histology"; "p16" AND "cytology;" "p16;" and "screening."

Are adjunctive markers useful in routine cervical cancer screening? Application of p16(INK4a) and HPV-PCR on ThinPrep samples with histological follow-up

The objectives of the study were to evaluate 1) the diagnostic sensitivity and specificity of p16(INK4a) as a marker for high-grade cervical lesions, 2) the results of a real-time polymerase chain reaction detecting high-risk human papillomavirus, and 3) the interobserver variability of the p16(INK4a) interpretation.A total of 232 ThinPrep samples were stained for p16(INK4a), and HPV-DNA PCR was performed on 107 specimens with inclusion of both benign and abnormal cytology. Histological follow-up information was collected. The diagnostic sensitivity of ASC+ with CIN2+ in histology as endpoint was 96% for p16(INK4a) and 100% for HR-HPV DNA PCR, and the diagnostic specificity was 41% and 27%, respectively. If p16(INK4a) had been used for triage of the ASC samples, then 18 patients (42%) could have been spared unnecessary follow-up procedures compared to six patients (21%) with the HR-HPV DNA test.