Prostate cancer is a common malignancy affecting men. Understanding this disease involves histology, the microscopic examination of tissue. Histology is a fundamental tool for diagnosing prostate cancer and characterizing its nature, providing insights into the presence of cancer and its potential behavior.
What is Histology in Prostate Cancer?
Prostate cancer histology involves the examination of prostate tissue samples under a microscope to identify cancerous cells. These tissue samples are typically obtained through a biopsy, frequently a transrectal ultrasound (TRUS)-guided biopsy. During this procedure, an ultrasound probe is inserted into the rectum to visualize the prostate gland, allowing for the precise collection of small tissue samples using a fine needle.
A pathologist prepares the collected tissue samples by thinly slicing them and mounting them on glass slides. These slides are then stained, commonly with hematoxylin and eosin (H&E), to enhance cellular visibility. The pathologist meticulously examines these stained slides under a light microscope to confirm the presence of cancer, specifically looking for abnormal architectural patterns of glands, loss of basal cells, and unusual nuclear features within the glandular lining cells. This microscopic assessment is the only way to definitively diagnose prostate cancer and distinguish it from benign conditions.
The Gleason Score Explained
The Gleason score is the primary grading system used to assess the aggressiveness of prostate cancer based on its microscopic appearance. Pathologists assign two primary grades, ranging from 3 to 5, to the two most common cell patterns observed in the biopsy sample. Grade 3 signifies cancer cells that still resemble normal prostate tissue, with well-defined, separate glands. As the grade increases, the cells appear more abnormal; Grade 4 indicates fused or poorly formed glands, while Grade 5 represents highly abnormal cells that grow in solid sheets or cords with no discernible glandular structures.
These two primary grades are then added together to form the overall Gleason score, which typically ranges from 6 to 10. For example, a score of 3+3=6 indicates a less aggressive cancer. A score of 3+4=7 means the most common pattern is Grade 3, but a significant portion is Grade 4, suggesting an intermediate level of aggressiveness. Conversely, a score like 4+3=7 indicates a more aggressive intermediate-risk cancer because the predominant pattern is Grade 4. Higher scores, such as 8, 9, or 10, signify increasingly aggressive cancers with a greater potential for rapid growth and spread.
The International Society of Urological Pathology (ISUP) introduced an updated Grade Group system (Grade Group 1-5) in 2014 to simplify the interpretation of Gleason scores for patients and clinicians.
- Grade Group 1: Gleason score of 6 (least aggressive).
- Grade Group 2: Gleason scores of 3+4=7.
- Grade Group 3: Gleason scores of 4+3=7.
- Grade Group 4: Gleason scores of 8.
- Grade Group 5: Gleason scores of 9 and 10 (most aggressive cancers).
How Histology Guides Prostate Cancer Management
The detailed information derived from the histological report, especially the Gleason score and the corresponding Grade Group, plays a significant role in guiding prostate cancer management decisions. Oncologists and urologists utilize these findings, alongside other diagnostic tests like PSA levels and imaging results, to formulate treatment plans. For instance, men with low-risk prostate cancer, typically defined by a Gleason score of 6 (Grade Group 1), may be suitable candidates for active surveillance. This approach involves regular monitoring with PSA tests, digital rectal exams, and repeat biopsies to track the cancer’s progression, potentially avoiding immediate aggressive treatments and their associated side effects.
Conversely, higher Gleason scores or Grade Groups, such as 7 (Grade Group 2 or 3) or above, often indicate more aggressive disease, necessitating immediate and more intensive interventions. Treatment options may include radical prostatectomy (surgical removal of the prostate gland) or various forms of radiation therapy. The histological findings also help predict the cancer’s prognosis and the likelihood of recurrence, allowing doctors to tailor follow-up schedules and consider additional therapies if needed.