Comparison of p53 immunohistochemical staining in differentiated vulvar intraepithelial neoplasia (dVIN) with that in inflammatory dermatoses and benign squamous lesions in the vulva

Background Differentiated vulvar intraepithelial neoplasia (dVIN), the precursor lesion to human papillomavirus (HPV)-independent vulvar squamous cell carcinoma (VSCC), can be difficult to distinguish from vulvar inflammatory dermatoses. p53 has been suggested to be a useful biomarker for dVIN, but the percentage, intensity and patterns of staining have not been well characterized in dVIN and its histologic mimics. Method We studied p53 immunohistochemical staining patterns in 16 dVIN cases and 46 vulvar non-neoplastic squamous lesions (12 lichen sclerosus (LS); 7 lichen simplex chronicus (LSC); 3 lichen planus (LP); 6 psoriasis (PSO); 13 spongiotic dermatitis (SPO); 5 candidiasis (CAN)). dVIN cases were adjacent to a p16-negative invasive VSCC in resection specimens. Results All dVIN cases demonstrated null-type or moderate-strong uniform p53 staining in over 70% of basal cells, with moderate to strong continuous parabasal staining extending to two-thirds of the epidermis. This was in contrast to weak or weak-moderate patchy p53 staining in the majority of other lesions. Moderate-strong and increased basal p53 staining (≥70%) was also observed in a subset of lichen sclerosus (5/12, 42%), lichen planus (1/3, 33%) and spongiotic dermatitis (36%, 4/11), however in all categories, this was limited to the basal layer and any staining in the parabasal layers was patchy. Conclusion Strong and uniform p53 staining of basal cells, extending into the parabasal layers, and a complete absence of staining (null-type) is useful in distinguishing dVIN from other mimics in the vulva. p53 staining of lesser intensity or quantity, particularly basal-overexpression only, overlaps with vulvar inflammatory lesions.