type VIN were strongly reactive to p16INK4 with a mean score of 5.5 (range 4-6, median ¼ 6), supporting their association with HPV ( Figure 1D).It is now generally accepted that there are at least two type of vulvar intraepithelial neoplasia (VIN): classic type VIN and simplex type VIN. Classic VIN is associated with HPV infection. 8 Currently, it is believed that simplex VIN is rarely associated with HPV infection. 4 In simplex VIN, p53 positive cells are often present above the basal cell layer whereas in classic VIN this does not occur. 4 Simplex VIN is also more frequently associated with well differentiated invasive squamous cell carcinoma.All of our classic VIN cases are strongly immunopositive with p16INK4 whereas 90% of our simplex VIN cases showed no reactivity to p16INK4 antibody. The remaining two cases exhibited focal weak positivity which may be considered negative in clinical practice, so that all of our classic VIN are positive and 100% of our simplex VIN are negative for p16INK4. Our study suggests that the immunohistochemical staining pattern of simplex VIN could thus be characterized as p16INK4 negative with p53 positive cells above the basal layer of the epidermis whereas classic warty type VIN is p16INK4 positive but negative for p53 in the supra-basilar layers.Our results affirm the current supposition that simplex VIN is usually a non-HPV-related lesion. Because of the higher rate of conventional invasive squamous cell carcinoma associated with simplex VIN, our findings support the premise that simplex VIN serves as a precursor to non-HPV-related invasive well differentiated squamous cell carcinoma of the vulva.