Aims The most commonly mutated gene in vulvar squamous cell carcinoma (VSCC) is TP53 and its prognostic value, particularly in HPV-independent VSCC, is uncertain. In other tumours, p53... Show moreAims The most commonly mutated gene in vulvar squamous cell carcinoma (VSCC) is TP53 and its prognostic value, particularly in HPV-independent VSCC, is uncertain. In other tumours, p53 immunohistochemistry (IHC) is an excellent surrogate marker for TP53 mutations. In order to study this in VSCC, we assigned six p53 IHC patterns into two final classes: 'wild-type' or 'mutant'. We determined the performance and interobserver variability of this pattern-based p53 IHC approach.Methods and results Two experienced gynaecological pathologists scored the predefined p53 IHC patterns of 59 VSCC, independently and blinded for molecular data. Agreement was calculated by Cohen's kappa. All disagreements regarding p53 IHC patterns were resolved by a consensus meeting. After DNA isolation, the presence of pathogenic TP53 variants was determined by next-generation sequencing (NGS). Sensitivity, specificity and accuracy of p53 IHC as a surrogate marker for TP53 mutation status were calculated. Initial p53 IHC pattern interpretation showed substantial agreement between both observers (k = 0.71, P < 0.001). After consensus, 18 cases (30.5%) were assigned a final p53 IHC class as TP53 wild-type and 41 cases (69.5%) as mutant. The accuracy between the p53 IHC class and TP53 mutation status, after the consensus meeting, was 96.6%. Moreover, the sensitivity and specificity were high 95.3% [95% confidence interval (CI) = 82.9-99.1% and 100% (95% CI = 75.9-100%)].Conclusions Pattern-based p53 IHC classification is highly reproducible among experienced gynaecological pathologists and accurately reflects TP53 mutations in VSCC. This approach to p53 IHC interpretation offers guidance and provides necessary clarity for resolving the proposed prognostic relevance of final p53 IHC class within HPV-independent VSCC. Show less
Vulvar cancer is a rare gynaecological malignancy, associated with either human papillomavirus (HPV) infections or genetic mutation(s) in the tumour suppressor gene TP53. This thesis consists... Show moreVulvar cancer is a rare gynaecological malignancy, associated with either human papillomavirus (HPV) infections or genetic mutation(s) in the tumour suppressor gene TP53. This thesis consists of two parts. In the first section we intended to investigate several important clinical issues in the treatment of vulvar cancer. We investigated the value of a tumour-free margin of minimal 8 mm for prevention of local recurrences and found that this margin can potentially be smaller than currently advised. Besides that, we researched the surgical treatment of the groins and found that patients with metastases in the groins can be safely treated by surgical removal of the enlarged lymph nodes followed by radiotherapy instead of extensive surgery of the groins. This can reduce treatment related morbidity in patients that need surgical treatment of their groins. The second part of this thesis focusses on the pathogenesis of vulvar cancer with an emphasis on HPV-independent vulvar cancers. Our research suggests a possible third subtype of vulvar cancer, the HPV-independent and TP53 wild type vulvar cancers. This further distinction possibly influences treatment and follow-up regimen for vulvar cancer patients. Show less
