A prostate biopsy is a medical procedure used to remove small tissue samples from the prostate gland to check for the presence of cancerous cells. This procedure is typically performed when a man has an elevated prostate-specific antigen (PSA) level in the blood or following an abnormal finding during a digital rectal examination (DRE). The purpose of the biopsy is to obtain tissue for microscopic analysis, which determines whether cancer is present and, if so, how aggressive it may be. Different approaches are used to collect these samples, utilizing specific guidance technology and access routes.
The Standard Approach: Transrectal Biopsy
The traditional method for tissue sampling is the Transrectal Ultrasound (TRUS) guided biopsy. This approach uses an ultrasound probe inserted into the rectum to create real-time images of the prostate gland, allowing the physician to visualize the borders and guide the needle accurately. The biopsy needle passes through the wall of the rectum into the prostate to collect thin cylinders of tissue, known as cores. This procedure relies on a systematic sampling pattern, typically involving 10 to 12 cores from predetermined areas across the gland. This systematic method aims to cover the entire prostate, as early-stage cancer may be too subtle to be seen on ultrasound alone.
A significant challenge with the transrectal route is the risk of infection. Passing the needle through the rectal wall introduces bacteria from the bowel into the prostate tissue. While antibiotics are administered, the increasing prevalence of antibiotic-resistant bacteria has led to concerns about post-biopsy infections, including sepsis.
Advanced Guidance: Targeted Biopsies
Targeted biopsies represent an advancement, moving beyond systematic sampling to focus on areas most likely to harbor cancer. This approach is driven by multiparametric Magnetic Resonance Imaging (mpMRI), which provides detailed images that identify suspicious lesions often missed by standard ultrasound. The high resolution of the MRI helps pinpoint specific areas for sampling.
The most common targeted method is the MRI-Ultrasound fusion biopsy. This technique involves electronically overlaying pre-procedure MRI images with real-time ultrasound images during the biopsy. This creates a precise, three-dimensional map that allows the physician to guide the needle directly to the suspected lesion. Targeted cores are generally taken from these suspicious areas, often in addition to systematic cores from the rest of the gland.
Suspicious areas identified on the MRI are scored using the Prostate Imaging-Reporting and Data System (PI-RADS). This system standardizes the reporting of prostate MRI findings, with scores ranging from 1 to 5. A score of 4 or 5 indicates a high likelihood of clinically significant cancer. This scoring helps determine which lesions warrant a targeted biopsy. Targeted biopsies can be performed using either a transrectal or a transperineal access route.
The Alternative Route: Transperineal Biopsy
The transperineal biopsy uses a distinct access route, passing the needle through the skin of the perineum—the area between the scrotum and the anus—instead of through the rectum. This method significantly reduces the risk of serious infection, as the needle bypasses the bacteria-rich environment of the rectal wall entirely. Studies have shown a near-zero rate of sepsis with this technique.
The procedure often requires sedation, though it can also be performed with local anesthesia. The transperineal route provides excellent access to the entire prostate, including the anterior (front) portion of the gland, which can be difficult to reach transrectally. This improved access is important because some aggressive cancers can be located in the anterior prostate.
The transperineal route is increasingly used in conjunction with advanced guidance, such as the MRI-fusion technique. Combining the low infection risk with the precision of MRI-fusion is becoming the preferred diagnostic strategy in many centers, maximizing both patient safety and the accuracy of cancer detection.
Understanding the Results: Pathology and Grading
Once the tissue samples are collected, they are sent to a pathology lab where a specialist examines them under a microscope. The pathologist analyzes the cell architecture and appearance to confirm the presence of cancer and determine its characteristics. This analysis defines the aggressiveness of any detected cancer.
The primary system used to describe the cancer’s grade is the Gleason Score, determined by summing the two most common patterns of cancer cells observed. Since cancer cells are graded on a scale of 3 to 5 based on how abnormal they appear, the final Gleason Score typically ranges from 6 (3+3) to 10 (5+5). A higher score indicates a more aggressive cancer.
The International Society of Urological Pathology (ISUP) introduced the Grade Group system to simplify and improve the prognostic accuracy of the Gleason Score. This newer system assigns a number from Grade Group 1 (least aggressive, Gleason Score 6) to Grade Group 5 (most aggressive, Gleason Scores 9 or 10). This standardized grading helps medical teams interpret the biopsy results and plan the appropriate management strategy.