In castration‐resistant prostate cancer, where FAP IHC often remains positive, including in prostate‐specific membrane antigen (PSMA)‐negative tumours, fibroblast activation protein inhibitor positron emission tomography (FAPI‐PET) can detect such lesions, highlighting FAP's complementary role to PSMA imaging in late‐stage disease [42, 45, 46]. The gene discussed is FOLH1; the disease is prostate cancer.