Prostate Cancer Getting Checked What Tests Might be Done Prostate Biopsy Cores of tissue (needel biopsies) are taken from your prostate for microscopic examination. About 12 biopsies will be taken from different parts of the prostate using the needle. The biopsies are usually taken through the back passage. You will be given a local anaesthetic and antibiotics. You will lie on your side with your knees up to your chest to expose your anus. An ultrasound probe will be inserted into your back passage to guide the needle. It can take up to 2 weeks to get the result of the microscopic examination. Biopsies are the most accurate way of diagnosing prostate cancer. Biopsies will help determine how aggressive the prostate cancer is. Biopsies will help determine the best treatment.