p16 Immunohistochemistry Is Not Always Required For Accurate Diagnosis of Grade 2 Squamous Intraepithelial Lesions

Comparison of Ki67 index and P16 expression in different grades of cervical squamous intraepithelial lesions

Background

the assessment of P16 expression and Ki-67 proliferative index is now proposed as an adjunct test for the diagnosis of high-risk precursor lesions for cervical cancer. The aim of the present study was to elucidate the quality expression of P16 and quantification Ki-67 index in different types of cervical intraepithelial neoplasia and also to determine the cutoff for Ki67 index to predict the severity of CIN lesions.

Methods

This cross-sectional study was conducted on patients with colposcopic indication. Selected samples with different CIN grades were examined for P16 and Ki-67 index by immunohistochemical (IHC) methods.

Results

All LSIL (CIN I) cases were negative for P16, while in 58.7% of HSIL cases (CIN 2/3), P16 was positive. The mean Ki67 index in the present study was 3.13 ± 2.65 in the upper two/third of the squamous epithelium in the LSIL group and 19.04 ±36.40 in the HSIL group, which was statistically significant. Also, the mean Ki67 index in full thickness squamous epithelium in HSIL group was significantly higher than LSIL. The sensitivity of P16 and Ki67 index in our study was 58.73%, 66.67% and the specificity was 100% and 100%, respectively.

Conclusion

Assessment of P16 expression and Ki67 index can be used to distinguish low grade (CIN1) intraepithelial lesion from high grade (CIN2/3) intraepithelial or precancerous lesions.

The CERTAIN Study Results: Adjunctive p16 Immunohistochemistry Use in Cervical Biopsies According to LAST Criteria

The Lower Anogenital Squamous Terminology (LAST) Project recommends the use of p16 immunohistochemistry as an adjunct to morphologic assessment of cervical biopsies according to a specific set of criteria. We analyzed the effect of adjunctive p16 according to LAST criteria in a US-based diagnostic utility study involving 70 surgical pathologists providing a total of 38,500 reads on cervical biopsies. Compared with the results obtained using hematoxylin and eosin-stained slides only, including p16-stained slides per LAST criteria increased sensitivity and specificity for diagnosing histologic high-grade squamous intraepithelial lesions across all cases by 8.1% (95% confidence interval [95% CI], 6.5-9.7; P<0.0001) and 3.5% (95% CI, 2.8-4.2; P<0.0001), respectively, using expert consensus diagnoses on hematoxylin and eosin+p16 as reference. Within the subset of cases classified by the pathologists as fulfilling the LAST criteria, adding p16 significantly increased both sensitivity (+11.8%; 95% CI, 9.5-14.0; P<0.0001) and specificity (+9.7%; 95% CI, 7.8-11.5; P<0.0001). However, a comparable improvement in sensitivity (+11.0%; 95% CI, 7.8-14.1; P<0.0001) was found when p16 was used in cases for which p16 staining was not ordered per LAST by the pathologists, whereas specificity decreased by -0.8% (95% CI, -1.1 to -0.5; P<0.0001). The study demonstrates a clinically and statistically significant increase in sensitivity and specificity for high-grade squamous intraepithelial lesion when p16 is used according to LAST criteria. Expanding the use of p16 into non-LAST cases would lead to a comparable improvement in sensitivity within this subgroup of biopsies, at the cost of a minimal, but statistically significant difference in specificity.

Analysis of factors affecting the prognosis of patients with cervical intraepithelial neoplasia 2

According to the 2014 World Health Organization Classification of Tumors of Female Reproductive Organs, patients with cervical intraepithelial neoplasia 2 (CIN2) have an equivocal diagnosis, but p16 is considered as the reference index for CIN2. Positive p16 expression in CIN2 is associated with high-grade squamous intraepithelial lesions (HSIL), whereas p16 negative lesions are low-grade squamous intraepithelial lesions. The purpose of the present study was to examine the clinical value of p16 and human papillomavirus (HPV) E6/E7 mRNA in the prognostication of patients with CIN2. From January 2013 to January 2016, 108 patients were diagnosed with CIN2 by biopsy and followed up at 6-month intervals at Peking University People's Hospital (Beijing, China). The expression of HPV E6/E7 mRNA was detected by in situ hybridization, while the expression of p16 and Ki-67 proteins was detected by immunohistochemistry. Of the 108 CIN2 cases, 20 progressed to HSIL/CIN3, 36 cases demonstrated persistence with CIN2 after the follow-up and 52 cases achieved regression (≤CIN1). Of the p16-positive 82 cases, 20 cases were detected to have progressed, whereas in the p16-negative group, no progression was observed. There were statistically significant differences among the p16-positive and negative groups (P<0.05). In the HPV E6/E7 mRNA-positive 69 cases, 18 cases were detected to have progressed, whereas in the HPV E6/E7 mRNA-negative 39 cases, progression was detected in only 2 cases. There were statistically significant differences among the HPV E6/E7 mRNA-positive and negative groups (P<0.05). The area under the receiver operating characteristics curve was plotted; the area under the curve for HPV E6/E7 mRNA was 0.745, that for p16 was 0.546 and that for Ki-67 was 0.501. The detection of HPV E6/E7 mRNA may provide important predictive information for the prognosis of CIN2, however p16 and Ki-67 proteins may provide little value.