Third, half of the cases in the present study had lymph node metastasis, but this may have been missed as our institutions (Ehime University Hospital and the National Hospital Organization Shikoku Cancer Center) did not have prostate-specific membrane antigen (PSMA)-positron emission tomography (PET), which detects where the prostate cancer cells are located in the body. This evidence concerns the gene FOLH1 and prostate cancer.