The risk of vulvar squamous cell carcinoma (VSCC) in patients with high‐grade vulvar intraepithelial neoplasia (VIN) is considered lower in high‐grade squamous intraepithelial lesion (HSIL) compared to differentiated VIN (dVIN), but studies are limited. Our study investigated both the incidence of high‐grade VIN and the cumulative incidence of VSCC in patients with HSIL and dVIN separately. A database of women diagnosed with high‐grade VIN between 1991 and 2011 was constructed with data from the Dutch Pathology Registry (PALGA). The European standardized incidence rate (ESR) and VSCC risk were calculated, stratified for HSIL and dVIN. The effects of type of VIN (HSIL vs dVIN), age and lichen sclerosis (LS) were estimated by Cox regression. In total, 1148 patients were diagnosed with high‐grade VIN between 1991 and 2011. Between 1991‐1995 and 2006‐2011, the ESR of HSIL increased from 2.39 (per 100 000 woman‐years) to 3.26 and the ESR of dVIN increased from 0.02 to 0.08. The 10‐year cumulative VSCC risk was 10.3%; 9.7% for HSIL and 50.0% for dVIN (log rank P < .001). Type of VIN, age and presence of LS were independent risk factors for progression to VSCC, with hazard ratios of 3.0 (95% confidence interval [CI] 1.3‐7.1), 2.3 (95% CI 1.5‐3.4) and 3.1 (95% CI 1.8‐5.3), respectively. The incidence of high‐grade VIN is rising. Because of the high cancer risk in patients with dVIN, better identification and timely recognition are urgently needed.

Aims: Adequate diagnosis of human papillomavirus (HPV)‐associated high‐grade squamous intraepithelial lesion (HSIL) and HPV‐independent vulvar intraepithelial neoplasia (VIN) is essential but can be challenging. We comprehensively characterized a large population‐based series of vulvar lesions, originally reported as high‐grade VIN, and assessed the cancer risk.Methods and results: Baseline high‐grade VIN of 751 patients were categorized by histopathological reassessment, integrating the results of immunohistochemistry (p16^INK4a, p53, Ki‐67) and HPV DNA testing. Integrated analyses resulted in 88.4% HPV‐associated lesions (77.0% HSIL, 10.9% low‐grade SIL [LSIL], and 0.4% vulvar squamous cell carcinoma [VSCC]), 10.9% HPV‐independent lesions (6.1% HPV‐independent VIN, 4.7% nondysplastic lesions, and 0.1% VSCC) and 1.1% inconclusive lesions. HSIL demonstrated p16^INK4a block‐positivity in 99.0%, increased Ki‐67 in ≥2/3rd of the epithelium in 93.6%, and HPV positivity in 99.6%. In HSIL, a p53 wildtype mid‐epithelial staining pattern was common (51.6%) while this was not observed in HPV‐independent lesions. HPV‐independent VIN harboured mutant p53 patterns in 65.2% and showed a wide morphological spectrum, ranging from differentiated to nondifferentiated (‘HPV‐associated‐like’, in 41.3%). Kaplan–Meier analyses showed a 10‐year cancer risk of 8.0% in HPV‐associated HSIL, 67.4% in HPV‐independent VIN/p53mutant, and 27.8% in HPV‐independent VIN/p53wildtype. Strikingly, the 10‐year cancer risk was 73.3% in HPV‐independent VIN with nondifferentiated (‘HPV‐associated‐like’) morphology.Conclusion: Immunohistochemistry by p16^INK4a and p53 is highly recommended for optimal categorization into HPV‐associated and HPV‐independent VIN, which is of utmost importance given the different cancer risk. The high cancer risk of HPV‐independent VIN underscores the need for surgical treatment and close follow‐up, especially in case of a p53 mutant pattern and/or nondifferentiated morphology.

Current clinical and histological classifications are unable to determine the risk of vulvar squamous cell carcinoma (VSCC) in high‐grade vulvar intraepithelial neoplasia (VIN), making prognostic biomarkers highly needed. We studied host‐cell DNA methylation markers in high‐grade squamous intraepithelial lesion (HSIL) and differentiated VIN (dVIN) without VSCC, in HSIL and dVIN adjacent to VSCC and in human papillomavirus (HPV) positive and negative VSCC, relative to control vulvar tissues. A series of 192 formalin‐fixed paraffin‐embedded vulvar samples, including VSCC (n = 58), VIN adjacent to VSCC (n = 30), VIN without VSCC during follow‐up (n = 41) and normal vulvar tissues (n = 63), were tested for 12 DNA methylation markers with quantitative multiplex methylation‐specific PCR (qMSP). HPV status was determined by p16^INK4A immunohistochemistry and high‐risk HPV PCR analysis. Logistic regression analyses were used to determine methylation patterns and methylation marker performance for VIN and VSCC detection. Methylation markers showed significantly higher methylation levels with increasing severity of disease. VIN adjacent to VSCC showed a similar methylation‐high pattern as VSCC, while VIN without VSCC displayed a heterogeneous methylation pattern. Vulvar carcinogenesis is associated with increased DNA methylation. Higher DNA methylation levels in VIN seem to reflect higher cancer risk, emphasizing the high potential of DNA methylation biomarkers in the diagnostic workup of VIN. As a next step, longitudinal studies are needed to verify the prognostic value of methylation biomarkers as a clinical tool for stratification of cancer risk in women with VIN.

Differentiated vulvar intraepithelial neoplasia (dVIN) is the precursor of human papillomavirus (HPV)-independent vulvar squamous cell carcinoma (VSCC). Given the rare incidence of dVIN, limited information on the exact cancer risk is available. We systematically reviewed the primary and recurrent VSCC risk in patients with dVIN, as well as the time to cancer development. A systematic search was performed up to July 2021 according to the PRISMA guidelines. Five reviewers independently screened articles on title, abstract and full text, followed by critical appraisal of selected articles using the Quality in Prognostic Studies (QUIPS) tool. Of the 455 screened articles, 7 were included for analysis. The absolute risk for primary VSCC in dVIN varied between 33 and 86%, with a median time to progression to VSCC of 9–23 months. The risk of developing recurrent VSCC in dVIN associated VSCC was 32–94%, with a median time to recurrence of 13–32 months. In conclusion, patients with dVIN have a high risk of developing primary and recurrent VSCC with a short time to cancer progression. Increased awareness, timely recognition, aggressive treatment and close follow-up of HPV-independent vulvar conditions including dVIN is therefore strongly recommended.

The precursor lesions of vulvar squamous cell carcinoma (VSCC) include human papillomavirus (HPV)‐associated and HPV‐independent squamous neoplasia with a varying cancer risk. Our study aimed to validate the accuracy of previously identified DNA methylation markers for detection of such high‐grade vulvar intraepithelial neoplasia (VIN). A large clinical series of 751 vulvar lesions, originally diagnosed as high‐grade VIN, were reassessed and categorized into HPV‐associated or HPV‐independent vulvar disease categories. Together with 113 healthy vulvar controls, all samples were tested for 12 methylation markers with quantitative multiplex methylation‐specific PCR (qMSP). Performance of individual markers and selection of an optimal marker panel for detection of high‐grade VIN was determined by logistic regression analysis. SST was the best‐performing individual marker (AUC 0.90), detecting 80% of high‐grade VIN cases, with excellent detection of HPV‐independent VIN (95%), known to have the highest cancer risk. Merely 2% of controls tested methylation positive for SST . Selection of a marker panel, including ZNF582 , SST and miR124‐2 , resulted in a comparably high accuracy for detection of high‐grade VIN (AUC 0.89). In conclusion, we clinically validated the accuracy of 12 DNA methylation markers for detection of high‐grade VIN. SST , as a sole marker or in a panel, provides an optimal diagnostic tool to distinguish high‐grade VIN in need of treatment, particularly HPV‐independent VIN, from low‐grade or reactive vulvar lesions. These findings warrant further prognostic validation of methylation biomarkers for cancer risk stratification of patients with VIN.

In patients with high-grade squamous intraepithelial lesion (HSIL) of the vulva, the presence of multiple lesions, called multifocal HSIL, is common. The aim of this exploratory study was to investigate biomarker expression profiles in multifocal HSIL. In total, 27 lesions from 12 patients with high-risk human papillomavirus (HPV)-positive multifocal HSIL were tested for HPV genotype, expression of p16^INK4a and Ki-67, and DNA methylation of six genes. HPV16 was found most commonly in 21 (77.8%) HSILs. In two (16.4%) patients, HPV genotype differed between the lesions. All lesions demonstrated diffuse p16^INK4a staining, of which three (11.1%) were combined with patchy staining. One patient (8.3%) demonstrated markedly different DNA methylation levels between lesions. Generally, heterogeneity in methylation profiles was observed between different patients, even when other biomarkers showed similar expression. In conclusion, this study is the first to demonstrate heterogeneity of individual lesions in patients with multifocal HSIL. The studied biomarkers have the potential to refine prognostic and predictive diagnostics. Future prospective, longitudinal studies are needed to further explore the potential of a biomarker profile for management of patients with multifocal HSIL.