The only prospective cohort study identified was by Cooper and Wojnarowska,8 who followed up 114 patients for a mean of 72 months. Vulval intraepithelial neoplasia preceded the development of vulval SCC in 1 patient. Squamous cell carcinoma occurred in another 2 patients, but the site affected was the perianal location in 1 and the oral location in 1. It was implied, although this was not explicitly stated, that both of these sites were affected by erosive lichen planus before the development of malignancy. Vulval intraepithelial neoplasia occurred in another 6 patients. There was no comment on HPV status, comorbidities, the duration or severity of disease, or the response to treatment in the affected individuals. The prevalence of SCC development (any site) for this cohort was calculated at 3% during 72 months.