Prostatic Intraepithelial Neoplasia

Prostatic intraepithelial neoplasia or PIN for short is a condition in which cells from the prostate begin to look and behave abnormally. Each year around 16% of men who undergo a prostate biopsy will find out they have PIN which is essentially a precancerous condition and therefore is not prostate cancer.

Where PIN begins

The abnormal cells of PIN begin and are located in two different areas of the prostate – one area is called acini which is the lining of tiny sacs that give the prostate its spongelike appearance.  These same sacs are responsible for producing the fluid that is mixed together with sperm helping to create semen. 

The second area PIN may be located in is in the lining of the ducts that carry this fluid to the main ejaculatory duct that reaches the penis.

As PIN develops, the epithelial cells lining the acini and the ducts look abnormal even though the lining itself remains intact.  This is different from prostate cancer in which the epithelial lining ruptures and the malignant cells penetrate into the tissue of the prostate gland.

How is PIN different from prostate cancer?

PIN has various differences from prostate cancer.  One difference is that it cannot be detected during a digital rectal exam.  Another way is that PIN does not cause PSA levels to rise as prostate cancer would.  The way it is diagnosed is either during a prostate biopsy or when a treatment for benign prostatic hyperplasia called transurethral resection of the prostate (TURP) is performed where prostate tissue is removed.

When this condition is discovered, it is given a grade of either low-grade PIN or high-grade PIN.  Low-grade PIN does not increase a man’s risk of prostate cancer as the abnormal cells are only slightly different from normal cells. 

High-grade PIN could increase the chance as the abnormality of the cells is more pronounced than in low-grade PIN.  This makes it more likely that high-grade PIN could lead to the development of prostate cancer. 

One reason for the increased risk is that high-grade PIN is usually found in the peripheral zone of the prostate where most cases of prostate cancer start.  Another reason is that 82% of prostate specimens with cancer also had areas of high-grade PIN while only 43% of those without prostate cancer. A third reason is that men with high-grade PIN have an increased risk for prostate cancer during a follow-up biopsy when compared to men with low-grade PIN or normal tissue.

Options for men with high-grade PIN

Because of the dilemma associated with high-grade PIN and the possible increased risk of going on to develop prostate cancer, doctors are often divided on what to recommend when it is discovered. 

Some doctors may recommend using the standard prostate cancer screening tests of the blood test for PSA, a digital rectal exam, transrectal ultrasound, and looking into family history of prostate cancer to evaluate the risk of progression.  But the issue with this is the test does not reliably help identify men who have high-grade PIN and who will go on to develop prostate cancer. 

This leaves open other options that a doctor may recommend after being diagnosed with PIN.  This might include a follow-up biopsy in three to six months or in six to 12 months or at three years.  Doctors who want to keep an extra close eye on high-grade PIN may recommend multiple biopsies done every three to six months for two years and then annually for life.

There is no one size fits all recommendations for every man with high-grade PIN.  If a man is diagnosed with high-grade PIN, he should  have a close working relationship with his doctor to determine the best way to manage it by doing a thorough evaluation of his risk profile to decide when a second biopsy should be done. 

Remember, high-grade PIN is not the same thing as prostate cancer – there is time to decide the course of action to take and in the meantime, look ahead to new treatment options in the future.