AR and Familial prostate cancer: Thus far, AR and neuroendocrine markers are the two most common and crucial histologic features helping to categorize CRPC into different phenotypes such as AR-high prostate cancer (ARPC); AR-low prostate cancer (ARLPC); neuroendocrine prostate cancer (NEPC); and both AR-null and NE-null CRPC, also named double-negative CRPC (DNPC) [28,30].