This correlation between HPV infection and the switch in SOX expression was found in 3 out of 13 cases (23.1%) of SIL where squamous metaplasia (characterized by a strong positive immunostaining for keratin 17 and keratin 7; Figure 5D,I) was found adjacent or in close proximity to SIL (see Table 3). This evidence concerns the gene KRT7 and squamous cell intraepithelial neoplasia.