When doctors talk about prostate cancer, they use something called the TNM system.  The “T” tells you the local extent of the tumor – how big it seems to be within the prostate, whether it has reached the border of the prostate, or whether it has spread locally into the nearby seminal vesicles (tiny organs that sit above the prostate like two wings; picture an apple with two leaves on top).  The “N” stands for the presence of any nearby metastases, or bits of cancer that have spread from the original site in the prostate to the lymph nodes, and the “M” is for distant metastases.  

When you get a biopsy, the pathologist comes up with the clinical stage.  This is the pathologist’s best guess of how much cancer you have, based on how much cancer was found in the biopsy cores, your PSA, MRI or other imaging, and what the Gleason grade of those cells was.  If you have surgery to remove the prostate, the doctors will have a lot more to work with – your entire removed prostate and tissue from the nearby lymph nodes.  This is called the pathologic stage, and it is definitive.  

What are the possibilities here?  You could have cancer confined to the prostate, called organ-confined cancer; cancer that has reached the outer wall of the prostate, called capsular penetration; positive surgical margins, which means cancer was found in the cells at the very edge of the surgical specimen (which includes the prostate and some surrounding tissue); invasion of the seminal vesicles; and involvement of the pelvic lymph nodes.

Here’s how that correlates to the TNM system:

Stage What it Means
T1a Cancer not palpable (able to be felt) in a rectal exam, and is found incidentally during a TUR procedure for BPH (benign enlargement of the prostate); cancer is in 5 percent or less of the removed tissue.
T1b Found incidentally, as in T1a, but greater than 5 percent of the tissue removed during the TUR is cancerous.
T1c Not palpable; found during needle biopsy due to elevated PSA.
T2a Palpable; involves less than half of one lobe of the prostate.
T2b Palpable; involves more than one half of one lobe, but not both lobes.
T2c Palpable; penetrates the wall of the prostate and/or involves the seminal vesicles
T3, T4 Palpable; penetrates the wall of the prostate and/or involves the
N+ Has spread to the lymph nodes.
M+ Has spread to bone.
Janet Farrar Worthington
Janet Farrar Worthington is an award-winning science writer and has written and edited numerous health publications and contributed to several other medical books. In addition to writing on medicine, Janet also writes about her family, her former life on a farm in Virginia, her desire to own more chickens, and whichever dog is eyeing the dinner dish.