Well PNI is still being debated and my understanding of its significance is as a predictor of more advanced disease and adverse features (EPE, SVI, high Gleason etc) at biopsy.
As Blackball has had an RRP and has clear margins he knows he no longer has PNI as it's in the bin. This paper Sums up some of the thinking
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3353268/