This study aimed to evaluate the immunophenotype of PIA lesions in dogs, establish a topographic relationship between normal, PIA and PC lesions, as well as to analyze TP53, MDM2, nuclear androgen receptor (AR) and PTEN protein and gene expression in PIA lesions, compared to normal prostates, in order to better characterize its preneoplastic potential in dogs. The gene discussed is MDM2; the disease is pachyonychia congenita.