High grade prostatic intraepithelial neoplasia (HG-PIN)

What is high-grade prostatic intraepithelial neoplasia (PIN)?

High-grade prostatic intraepithelial neoplasia (PIN) is a non-cancerous condition that starts in the prostate gland. In this condition, abnormal prostate cells fill the small glands and ducts in the prostate. The diagnosis of high-grade PIN is not the same as having prostate cancer.  As a result, definitive treatment, such as surgery or radiation therapy, is not required for patients with high-grade PIN. A low-grade PIN also exists but it should not appear in pathology reports as it has been shown to have no clinical significance.

What is the prostate?

The prostate is a small organ that is found only in males.  The prostate is normally the size and shape of a walnut.  It is located at the bottom of the bladder and sits between the pubic bone (the front part of the hip) and the rectum.  The prostate also wraps around the urethra. The urethra is the tube that conducts urine from the bladder and semen from the ejaculatory ducts to the exterior of the body.

The prostate acts to secrete a fluid that helps nourish and transport sperm that comes from the testicles.  This fluid is made in by a complex network of small structures called glands and is then transported out of the prostate through channels called ducts.

Prostate biopsies

A biopsy is usually performed if abnormalities are detected in the prostate on digital rectal exam (DRE), if there is a family history of prostate cancer, or if the prostate-specific antigen (PSA) blood test reveals high levels. Most biopsies include multiple samples of tissue (typically 10 – 15) taken from various parts of the prostate.

How does a pathologist make the diagnosis of high-grade PIN?

The abnormal cells in high-grade PIN are located in the glands and ducts of the prostate. Unlike cancer cells, the abnormal cells in high-grade PIN are still separated from the surrounding tissue by a thin barrier.  When viewed under the microscope, the abnormal prostate cells are larger than normal prostate cells, their nuclei are darker (hyperchromatic), and prominent round structures called nucleoli can be seen in the center of the nucleus.

What is the significance of detecting high-grade PIN on prostate biopsy?

Some medical studies have suggested that the presence of high-grade PIN is associated with an increased risk of developing prostate cancer.  However, high-grade PIN does not always progress to prostate cancer and the likelihood of it progressing to cancer is much less than it was once thought.

How is high-grade PIN managed?

Experts are divided as to what type of medical follow-up is recommended when high-grade PIN is detected on biopsy.  It is generally accepted that other factors should be evaluated when determining when and if a repeat biopsy should be performed.  Talk to your doctor to determine the management strategy that is best for you.

by Trevor A. Flood, MD FRCPC (updated July 11, 2021)
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