Using a carcinogen-induced skin tumorigenesis mouse model, Balbin et al. reported in 2003 that the absence of MMP-8 dramatically increased the incidence of skin papillomas in male Mmp8-null mice, while a similar observation for tongue squamous carcinomas was made by Korpi et al. a few years later [10,13]. Here, MMP8 is linked to skin papilloma.