Prostate Biopsy Sampling
How many samples are taken in a prostate biopsy?
A sextant or 6-core biopsy scheme used to be the standard approach where 6 samples are taken systematically from the prostate. The 6 core samples included one each from the base, mid-gland, and apex on either side.
The currently recommended scheme for biopsy is the extended-pattern biopsy which involves taking 12 core samples systematically. In addition, further samples are taken from any lesion that is detected upon a digital rectal examination or ultrasound.
A saturation biopsy scheme (only when indicated) involves taking 30-50 core specimens. Seminal vesicles also may be included in the biopsy in some high risk patients.
What is done with the biopsy sample?
The tissue samples from the prostate biopsy are examined by a pathologist under a microscope for cancer cells.
If the biopsy sample reveals no cancerous cells, it could mean either the person does not have prostate cancer, or the prostate biopsy probably missed the tumor foci.
If the pathologist finds cancer cells, the next step is to find the Gleason score which is needed in grading the tumor. The relevance of this is discussed in detail under Cancer Staging and Grading.
Gleason grading evaluates the structural patterns of individual cancer glands. Five distinct patterns of growth are described. This includes well differentiated to poorly differentiated, with pattern 1 denoting the most differentiated, whereas pattern 5 stand for the most undifferentiated and with loss of the glandular architecture.
The final Gleason score is the sum of the grades of the most common, and second most common growth patterns. The total Gleason score can range from 2 to 10. The further management is planned based on the Gleason score.
Repeat Prostate Biopsy Tests
Patients with negative biopsy results are typically followed up conservatively with serial PSA levels and annual digital rectal examinations. A repeat biopsy is performed when PSA levels are persistently rising, if the initial biopsy is deemed inadequate or if DRE shows new nodularity or induration.
Refer to the article on When to biopsy prostate? for more information on guidelines for considering a repeat biopsy.
Complications of Prostate Biopsy
Patients undergoing transrectal prostate biopsy may pass some blood through the rectum (hematochezia) and in the urine (hematuria) for a few days after the procedure. Some blood in semen (hematospermia) for 2-3 weeks (less frequently up to 1-2 months) may be noticed.
Pain and Discomfort
Pain is usually minimal in patients who have anesthesia for the prostate biopsy procedure. The patients who undergo transperineal biopsy may experience some tenderness over the area of the procedure for few days. Pain and tenderness is more common in saturation biopsy requiring analgesics for about a week. Avoiding stress and straining immediately after the procedure will reduce the associated unpleasant feelings.
Serious infections like septicemia or an abscess are infrequent when proper sterile precautions are observed and with preventive antibiotic treatment. Infections are associated with increasing pain and tenderness or a high fever.
Inability to pass urine (common in saturation biopsy) may require the insertion of a catheter till the inflammation leading to the retention subsides but most of the time it is self-limiting.
High fever, excessive bleeding, increasing pain and tenderness, or inability to urinate after the procedure, should be immediately reported to the urologist.
Can prostate biopsy lead to spread of the tumor?
Theoretically cancer cells can spread through the biopsy needle tract. When there is a long tract for the needle to pass through from skin to the biopsy site, it would also mean that there is a long way back from the tumor to the skin surface. Such biopsies have higher chances for the cancer cells to drop off the needle and grow along the needle tract.
The needle tract for a transrectal prostate biopsy is extremely short since the biopsy needle goes through the rectal wall directly into the prostate. The chances of such spread is therefore extremely low. A remote risk of tumor spread may be attributed to the transperineal type of prostate biopsy, which is not a method that is commonly used these days. All patients in such reported instances of transperineal needle track spread had advanced stages prostatic cancer and Gleason score was high at the time of biopsy.
Overall reposts of cancer spread due to a prostate biopsy appear to be highly exaggerated. A prostate biopsy is an integral tool in identifying, assessing and managing prostate cancer. The benefits of this procedure should always be taken into consideration before refusing the biopsy due to unfounded claims.