@happyending01, a few people in the prostate cancer, pancreatic cancer and breast cancer groups have mentioned perineural invasion, for example here:
- Breast Cancer and Perineural Invasion
https://connect.mayoclinic.org/discussion/breast-cancer-and-perineural-invasion/
Keep in mind that chemotherapy is systemic, meaning it send the drugs through your entire body. So the chemotherapy drugs will treat not only the tumor but also the small nerves around the tumor - the perineural invasion.

When do you start FOLFOX treatment?