AR and neoplasm: For instance, commonly diagnostically tested prostate specific antigen (PSA) and prostate cancer antigen 3 (PCA3) may be complemented by the analysis of circulating tumor cells (CTCs), circulating tumor nucleic acids (ctDNA and ctRNA), or exosomes for molecular biomarkers, such as the AR-variant 7 (AR-V7) [16,17,18,19].