To investigate the clinical relevance of the PTEN-ARID4B-PI3K axis in prostate cancer, we performed immunohistochemical staining with antibodies against ARID4B, PTEN, and p110α on tissue microarrays (TMAs) consisting of 118 prostate adenocarcinoma samples from 85 patients and 73 prostate hyperplasia samples from 36 patients. The gene discussed is PIK3CA; the disease is Familial prostate cancer.