Extraprostatic extension and seminal vesicle invasion

The prostate has no true capsule, so extraprostatic extension means tumour beyond the boundary of the gland into the surrounding fat or the nerve bundles, and it makes the tumour T3a; the eighth edition of TNM added microscopic bladder neck involvement to the same category. Invasion of the muscular wall of a seminal vesicle is T3b. Invasion into the apex of the prostate, or into but not beyond the capsule, is explicitly not T3 and stays T2. A tumour fixed to or invading the rectum, the external sphincter, the levator muscles or the pelvic wall is T4.

On a radical prostatectomy report these sit beside the surgical margin status, which is a different question: extension describes how far the cancer grew, a positive margin describes whether the surgeon's cut passed through cancer, and a man can have one without the other. Extraprostatic extension, seminal vesicle invasion and a positive margin are the findings that raise the chance of PSA returning after surgery and that drive the discussion about adjuvant or early salvage radiotherapy. In the Cambridge Prognostic Groups, any T3 puts a man in group 4 on its own, and T4 puts him in group 5 on its own.