Role of the Biomarker p16 in Downgrading -IN 2 Diagnoses and Predicting Higher-grade Lesions

Abstract

In 2012, the College of American Pathologists and American Society for Colposcopy and Cervical Pathology published the "LAST" recommendations for histopathology reporting of human papilloma virus-related squamous lesions of the lower anogenital tract, including the use of a 2-tier nomenclature (low-grade squamous intraepithelial lesion/high-grade squamous intraepithelial lesion [LSIL/HSIL]) and expanded use of the biomarker p16 to classify equivocal lesions as either precancer (HSIL) or low-grade lesions (LSIL)/non-human papilloma virus changes. We aimed to determine (1) the frequency with which the poorly reproducible diagnosis of intermediate-grade (-IN 2) lesion in the lower anogenital tract would be downgraded on the basis of p16 results, and (2) whether p16 status was predictive of subsequent higher-grade lesions. A total of 200 specimens diagnosed as an intermediate-grade (-IN 2) lesion of the cervix (168), vagina (2), vulva (2), and anus (28) were reviewed and immunostained for p16. Slides were independently reviewed by 2 pathologists, with discrepant p16 interpretations adjudicated by a third pathologist. Of the 200 cases, 32% were negative for p16. Among the 166 patients with subsequent pathology (including 131 excisions), 26.2% of p16-positive cases versus 4.4% of p16-negative cases were associated with a subsequent diagnosis of HSIL (-IN 3) or worse (P=0.002). Reproducibility of the biopsy diagnosis was fair, with no significant difference with the addition of p16 or using 2 versus 3 tiers. In 11.5% of cases, there was discordance in p16 interpretation (κ 0.735, good agreement). The results indicate that using the Lower Anogenital Squamous Terminology recommendations would result in approximately one third of equivocal (-IN 2) diagnoses being downgraded to LSIL over 1 year in a busy academic practice. The significant association of p16 expression with a higher risk for HSIL on a subsequent specimen suggests that use of p16 to adjudicate equivocal (-IN 2) diagnoses in lower anogenital tract specimens as either LSIL or HSIL would likely predict lesion grade more accurately and avoid unnecessary excisional procedures.

Potential influence of p16 immunohistochemical staining on the diagnosis of squamous cell lesions in cervical biopsy specimens: observation from cytologic‐histologic correlation

“…9,18,27,28 Differentiating CIN2 from p16-positive CIN1 is a dubious process, in terms of both morphology and clinical significance. Although 1 study contends that p16 IHC may result in CIN2 being downgraded, 10 others (including the current study) argue that it can lead to increased upgrading of LSIL to HSIL. 11 Our study demonstrated more frequent LSIL diagnoses on follow-up LEEP/cone excisions for cases in which an HSIL diagnosis on the previous biopsy was aided by a positive p16 IHC result, suggesting potential overcall of some of those cases.…”

“…The literature postulates that widespread application of p16 IHC might result in either upgrading or downgrading of squamous cell lesions in cervical biopsy specimens. 10,11 In recent years, our laboratory's CHC has reflected an increase in discrepancies between cytologic LSIL and the follow-up histologic diagnosis, with an increase in HSIL being diagnosed on cervical biopsy. We hypothesize that the increase in use of p16 IHC in cervical biopsy specimens may have contributed to the increase in the discrepancies.…”

p16 immunostaining in histological grading of anal squamous intraepithelial lesions: a systematic review and meta-analysis

“…Most of them were conducted in USA (10 studies) [6,7,[15][16][17][18][19][20][21][22], two were performed in Germany [23,24], and one study each in Spain [25], Portugal [26], and Ireland [27]. Six did not describe the population from which ASIL samples were obtained [7,[16][17][18][19]22]. One study included only inflammatory bowel disease patients [21] and another included only hemorrhoidectomy specimens [6].…”

“…There is, however, information on the clinical impact of downgrading -IN2/AIN2 samples and the prognosis of -IN2/AIN2 samples based on p16 immunostaining. Albuquerque et al [26] showed that 34% of AIN2 are p16 negative, while Maniar et al [19] found 50% of AIN2 to be p16 negative in their respective populations. Albuquerque et al [26] study further demonstrated that the AIN2 p16-negative samples showed lower rates of progression in the follow-up with high-resolution anoscopy.…”

Moving forward—the 2019 ASCCP Risk-Based Management Consensus Guidelines for Abnormal Cervical Cancer Screening Tests and Cancer Precursors and beyond: implications and suggestions for laboratories

“…Pathologists give more consistent diagnoses on cervical biopsies with the judicious use of p16 IHC. Improved interobserver agreement for the diagnosis of CIN 2þ with the conjunctive use of hematoxylin and eosin (H&E) morphology and p16 IHC compared with H&E morphology alone has been shown in several studies, [35][36][37][38] including in a systematic review and meta-analysis. 39 Because histologic HSIL is the usual trigger for treatment, the use of p16 per the LAST and WHO guidelines provides our clinical colleagues more reproducible diagnoses upon which to base management recommendations.…”