p16 Is Superior to ProEx C in Identifying High-grade Squamous Intraepithelial Lesions (HSIL) of the Anal Canal

Abstract

Although the incidence of human papillomavirus (HPV)-associated anal neoplasia is increasing, interobserver and intraobserver reproducibility in the grading of biopsy specimens from this area remains unacceptably low. Attempts to produce a more reproducible grading scheme have led to the use of biomarkers for the detection of high-risk HPV (HR-HPV). We evaluated the performance of standard morphology and biomarkers p16, ProEx C, and Ki-67 in a set of 75 lesions [17 nondysplastic lesions, 23 low-grade squamous intraepithelial lesions (LSIL)/condyloma, 20 high-grade squamous intraepithelial lesions (HSIL), 15 invasive squamous cell carcinomas] from the anal and perianal region in 65 patients and correlated these findings with HPV subtype on the basis of a type-specific multiplex real-time polymerase chain reaction assay designed to detect HR-HPV. A subset of cases with amplifiable HPV DNA was also sequenced. HSIL was typically flat (15/20), and only a minority (4/20) had koilocytes. In contrast, only 1 LSIL was flat (1/23), and the remainder were exophytic. The majority of LSIL had areas of koilocytic change (20/23). HR-HPV DNA was detected in the majority (89%) of invasive carcinomas and HSIL biopsies, 86% and 97% of which were accurately labeled by strong and diffuse block-positive p16 and ProEx C, respectively. LSIL cases, however, only infrequently harbored HR-HPV (13%); most harbored low-risk HPV (LR-HPV) types 6 and 11. Within the LSIL group, p16 outperformed ProEx C, resulting in fewer false-positive cases (5% vs. 75%). Ki-67 was also increased in HR-HPV-positive lesions, although biopsies with increased inflammation and reactive changes also showed higher Ki-67 indices. These data suggest that strong and diffuse block-positive nuclear and cytoplasmic labeling with p16 is a highly specific biomarker for the presence of HR-HPV in anal biopsies and that this finding correlates with high-grade lesions.

Grading of atypia in genital skin lesions: routine microscopic evaluation and use of p16 immunostaining

“…Past studies have also showed that HSIL is not always p16 positive; accordingly, p16 immunostaining should not be performed when the diagnosis of HSIL can be made on routine staining. 4,10,11 While a lack of p16 immunoreactivity is seen in most normal cells (which have p16 expression that is low at the mRNA and protein levels), in some cases, lack of p16 immunostaining could represent inactivation of the gene by deletion or methylation. 20,21 This study confirms the high degree of subjectivity involved in grading dysplasia in genital skin lesions.…”

“…This recommendation for p16 immunostaining of equivocal lesions presumes an ultimate diagnosis of low‐grade squamous intraepithelial lesion (LSIL) for negative p16 staining and high‐grade squamous intraepithelial lesion (HSIL) for positive p16 staining in a case of ‐IN 2 . However, the role of p16 staining for aiding in evaluation of a wider spectrum of nonmucosal atypical genital skin lesions remains understudied . In order to narrow this knowledge gap, we sought to investigate the utility of p16 staining in the diagnosis of atypical genital skin lesions.…”

Utility of Human Papillomavirus Capsid Protein L1 and p16 in the Assessment and Accurate Classification of Anal Squamous Intraepithelial Lesions

“…4 p16 protein expression has been shown to be better than several other markers tested to date to confirm a diagnosis of HPV-related anal HSIL. 7,8,19 Several studies have shown that diffuse and strong nuclear or nuclear and cytoplasmic p16 expression strongly correlates with high-grade dysplasia, while focal or patchy nuclear staining may be seen in reactive epithelium and LSILs. 7 dysplasia), when there is diagnostic disagreement regarding the grade of dysplasia, or in samples that show changes that mimic true dysplasia (immature squamous metaplasia, sectioning artifact, atrophy, and reparative epithelial changes).…”

An update on anal neoplasia

“…In histological specimens, especially on HRA‐obtained biopsies, p16 protein expression has been shown to be superior to all other markers tested to date, including Ki‐67 and ProEx‐C, to confirm a diagnosis of HPV‐related anal HSIL . The same indications and interpretation criteria can be applied in anal lesions as in cervical lesions.…”

“…In histological specimens, especially on HRAobtained biopsies, p16 protein expression has been shown to be superior to all other markers tested to date, including Ki-67 and ProEx-C, to confirm a diagnosis of HPV-related anal HSIL. [38][39][40] The same indications and interpretation criteria can be applied in anal lesions as in cervical lesions. A p16-positive result is defined as a strong and diffuse nuclear or nuclear-plus-cytoplasmic staining of the basal cell layers involving at least one-third of the epithelial thickness ( Figure 6).…”