Role of Immunohistochemical Analysis of p16 and p53 in Vulvar Carcinoma

Tumor human papillomavirus (HPV) status is an important prognostic factor in vulvar cancer as indicated in the latest WHO classification of female genital tract tumors. Immunohistochemical detection of p16 is well established as a surrogate biomarker for tumor HPV association, including squamous cell carcinomas of the vulva. HPV-independent vulvar carcinomas are heterogeneous with 2 subcategories according to the TP53 mutation status. Therefore, the simultaneous use of p53 and p16 immunohistochemistry is recommended for accurate subclassification of vulvar squamous cell carcinomas. However, the role of molecular analytical tools, in particular RNA ISH and TP53 sequencing, is not so clear. This study aimed to investigate the performance of p53 and p16 immunohistochemistry for the diagnosis of vulvar carcinomas in comparison to TP53 mutation analysis and HPV RNA ISH. We analyzed 48 vulvar carcinomas in a tissue microarray format. Sensitivity and specificity for both methods, p16 (100% and 96%) and p53 (95% and 90%) immunohistochemistry for detection of HPV association as well as for TP53 mutations was high. Combining p16 and p53 immunohistochemistry we correctly classified all carcinomas in our series according to current WHO criteria. The sensitivity of HPV RNA ISH for the detection of HPV association was lower compared to p16 immunohistochemistry. Rare HPV-associated cases with TP53 mutation and HPV-independent tumors with p16 overexpression are discussed. In summary, the combined use of p16 and p53 immunohistochemistry for subclassification of vulvar carcinomas is justified in daily practice. Molecular tests should be restricted to rare cases with ambiguous clinicopathologic or immunohistochemical features.