In the era of comparative oncology and given that the dog is the only other known large mammalian species to spontaneously develop prostate cancer [25], there exists scientific justification for investigating PSMA expressions in canine prostate cancer and other solid tumors, with the potential to advance PSMA theragnostic strategies to benefit pet dogs and lay the groundwork for future human applications. This evidence concerns the gene FOLH1 and Familial prostate cancer.