A prostate biopsy is a medical procedure involving the removal of small tissue samples from the prostate gland using a fine needle. This procedure is the definitive method for determining if cancer cells are present within the gland. A biopsy is typically needed after preliminary screening tests, such as an elevated Prostate-Specific Antigen (PSA) blood test result or an abnormality detected during a digital rectal exam (DRE).
The Standard Transrectal Biopsy
The Transrectal Ultrasound-Guided (TRUS) biopsy was historically the most common approach for tissue acquisition. This method involves inserting a specialized ultrasound probe into the rectum to visualize the prostate gland. The probe then guides a spring-loaded needle through the rectal wall and into the prostate.
The physician performs a systematic sampling, taking multiple core tissue samples, often between 10 and 12, from various zones of the gland. Because this method relies on a systematic grid rather than specific targets, it is sometimes referred to as a “blind” biopsy.
The risk of infection is a major concern with the transrectal approach. Since the needle passes through the rectal wall, it can carry bacteria from the bowel directly into the prostate and bloodstream. Although prophylactic antibiotics are administered, this pathway presents a risk of serious infection, including sepsis, which may require hospitalization.
The Transperineal Biopsy Method
The Transperineal Biopsy Method is an alternative that addresses the infection risk by routing the needle through the skin of the perineum, the area between the scrotum and the anus. The physician disinfects the perineal skin, creating a sterile entry point that completely bypasses the bacteria-rich environment of the rectum.
This method offers a substantially lower rate of sepsis and near-elimination of serious post-biopsy infectious complications compared to the transrectal approach. Transperineal access also provides better reach to the anterior (front) region of the prostate, where tumors can sometimes be missed by the rectal approach.
The procedure is guided by an ultrasound probe placed in the rectum, but the needle never penetrates the rectal wall. Because this method requires multiple needle passes through the skin and deeper tissue, it is typically performed under mild sedation or general anesthesia to ensure patient comfort.
MRI Fusion Technology for Targeted Sampling
MRI Fusion Technology is a sophisticated guidance tool that can be applied to either access method. This technology represents a significant advancement in diagnostic precision, moving beyond the systematic sampling of the past. It begins with a pre-biopsy Multiparametric MRI (mpMRI) scan, which can identify suspicious lesions within the prostate tissue.
During the biopsy, previously captured MRI images are digitally merged, or overlaid, with real-time ultrasound images. Advanced software aligns the two image sets, compensating for the prostate’s movement and shape changes. This creates a detailed, three-dimensional map that allows the physician to see the suspicious lesion, which is often invisible on ultrasound alone, directly on the screen.
This precise targeting allows the physician to focus biopsy cores directly into the suspicious areas identified by the MRI. This is done in addition to or instead of the systematic core samples, increasing the detection rate for clinically significant cancers. The ability to precisely target lesions is particularly important for tumors located in hard-to-reach areas, such as the anterior portion of the prostate, which are often missed by non-targeted methods.
Interpreting Biopsy Results
Tissue samples are sent to a pathologist who examines them under a microscope to create a pathology report. If cancer is found, the report includes a grading system to describe the aggressiveness of the cancer cells. This description helps determine the likelihood of the cancer growing quickly or spreading.
The Gleason Score
The traditional measure is the Gleason Score, determined by evaluating the two most prevalent patterns of cancer cells in the sample. The pathologist assigns a grade from 3 to 5 to each pattern. These two numbers are added together to create a score, typically ranging from 6 to 10. For example, a score of \(3+4=7\) means the most common pattern is grade 3 and the second most common is grade 4.
The Grade Group System
A simplified Grade Group System has been widely adopted to translate the Gleason Score into five groups, numbered 1 through 5. Group 1 corresponds to a Gleason Score of 6, representing the least aggressive cancers. Group 5 includes the highest Gleason Scores, indicating the most aggressive disease.