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Performance of the pattern based interpretation of p53 immunohistochemistry as a surrogate for TP53 mutations in vulvar squamous cell carcinoma
INTRODUCTION:
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 tumors, 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: 'wildtype' or 'mutant'. We determined the performance and interobserver variability of this pattern-based p53-IHC approach.
METHODS:
Two experienced gynecologic 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 were determined by next-generation sequencing (NGS). Sensitivity, specificity, and accuracy of p53-IHC as a surrogate marker for TP53 mutation status...
Show moreINTRODUCTION:
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 tumors, 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: 'wildtype' or 'mutant'. We determined the performance and interobserver variability of this pattern-based p53-IHC approach.
METHODS:
Two experienced gynecologic 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 were determined by next-generation sequencing (NGS). Sensitivity, specificity, and accuracy of p53-IHC as a surrogate marker for TP53 mutation status were calculated.
RESULTS:
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 wildtype 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%CI 82.9-99.1%) and 100% (95%CI 75.9-100%)).
CONCLUSIONS:
Pattern-based p53-IHC classification is highly reproducible amongst experienced gynecologic 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- All authors
- Kortekaas, K.E.; Solleveld-Westerink, N.; Tessier-Cloutier, B.; Rutten, T.A.; Poelgeest, M.I.E.; Gilks, C.B.; Hoang, L.N.; Bosse, T.
- Date
- 2020-04-01
- Journal
- Histopathology
- Volume
- 77
- Issue
- 1
- Pages
- 92 - 99