Perineural Invasion in a Prostate Biopsy Specimen Is Not the Same as PNI in Prostatectomy Specimen

Categories: Spring 2007

Background: Many pathologists who examine prostate cancer biopsies believe that perineural invasion* (PNI) is present in all radical prostatectomy specimens if a careful search is made.

For this reason, some pathologists do not even report the presence or absence of PNI in needle biopsy specimens, thereby not distinguishing a needle biopsy specimen from a prostatectomy specimen.

However, many clinical doctors view the finding of PNI in a biopsy specimen as an adverse feature in prognosis.

The Johns Hopkins group is now excluding men with PNI on biopsy from their active monitoring possibility.

Question: What is the association of PNI with extracapsular tumor extension** (ECE) in our group of radical prostatectomy patients?

What We Found: Perineural invasion in the biopsy specimen is associated with a significantly greater risk of ECE.

Men with PNI should not be treated with active monitoring, and careful consideration should be given to whether the surgeon should attempt to spare the nerve on the side of the prostate that shows perineural invasion.

In this case, the potential benefits of nerve-sparing surgery should be strongly weighed against the greater risk of ECE.

Pathologists should continue to report this finding in prostate needle biopsy specimens since it has significance for prognosis and can influence treatment recommendation.

Study: From 2003 to 2006, we were able to document the presence or absence of PNI in the biopsy report for 789 radical prostatectomy patients operated on by Dr. Catalona. 127 men had PNI in the biopsy specimen and ECE was reported in 44% of these men. Only 14% of the men without perineural invasion had ECE.

*Small nerve fibers in the prostate gland secrete a growth factor that attracts prostate cancer cells, so when pathologists look at sections of the prostate gland, they frequently see the tumor cells surrounding the nerve fibers. This is called perineural invasion.

* Extracapsular tumor extension means that tumor cells are seen growing in the tissue surrounding the prostate. It is possible to have extracapsular extension with negative (clear) margins if a rim of additional tissue is removed with the prostate gland. However, it is also possible to have extracapsular extension with positive (cancerous) surgical margins. In either case, the risk for tumor recurrence is higher than if the cancer were completely contained within the prostate gland, but the risk is higher when there are both extracapsular extension and positive surgical margins.

Christopher R. Griffin, Chicago, IL; Stacy Loeb, MD, Washington DC; John Cashy, PhD; William J. Catalona, MD, Chicago, IL

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