The role of perineural space invasion in the local spread of prostatic adenocarcinoma.

In 176 radical prostatectomy specimens areas of capsule penetration by cancer and positive surgical margins were quantified and located over the prostate surface. The presence of cancer within the perineural space was sought in these areas and compared to the normal distribution of prostatic nerve branches. Capsule penetration was found in 78 of 156 stage B carcinomas, and in 39 of these 78 (50 per cent) it occurred entirely by cancer extension through the capsule within perineural spaces. In the remaining 39 prostates capsule penetration by perineural space invasion predominated but direct spread also was found. Most often, perineural space invasion followed the oblique vertical course of nerve branches that extended superiorly to the superior pedicle near the prostate base. In such cases capsule penetration areas were localized near the superior margin of the cancer, and in 11 per cent positive superior pedicle margins resulted from continued perineural space invasion outside the capsule. In cancers near the prostate apex capsule penetration by perineural space invasion produced positive margins in 89 per cent of 18 cases because of the short inferior pedicle. The role of perineural space invasion by cancer was less prominent in 4 of 20 stage A cancers that showed capsule penetration.