Although in earlier studies, PTEN was reported to be a protein exclusively localized in the cytoplasm; nowadays, it is clear that PTEN can be both cytoplasmic and nuclear, as widely demonstrated in normal canine tissues and tumors such as hemangiosarcoma, melanoma, and mammary carcinomas [24,27,28,30], as well as in human gliomas [17,41,44]. The gene discussed is PTEN; the disease is melanoma.