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Interview With An Expert: Why the Biopsy Is Not Perfect

Your prostate feels like a pincushion, and you’ve been waiting for the biopsy results. They’re finally here. Now what?

That’s a good question. You might think that the diagnosis of prostate cancer would be a fairly straightforward thing – especially if you’ve been through several biopsies and watched your PSA go up while it took months for the doctors to find the cancer that you suspected was in there.

But it may not be that straightforward. Here are a couple of things you need to understand about the prostate: It is a perplexing mix of different kinds of cells. It is the jambalaya of the pathology world.

Also, the biopsy – taking samples of tissue with a hollow-core needle for the pathologist to study under the microscope only provides an imperfect look at what’s inside the prostate. Imagine you are trying to see inside a locked house, and you can only look through a dozen peepholes, a few on each wall. It sounds like the setup for a bad riddle, but that’s pretty much what the biopsy is like. If the only way to try to locate cancer is through tiny holes, the odds of missing it at any given time are fairly high.

Biopsy is better now than it used to be: Not too long ago, doctors used to take just samples from the prostate; then they started taking six. Now they take 12, which sounds like a lot, although actually it’s not that much more. “These are tiny pieces of tissue,” says Johns Hopkins urologic pathologist Angelo M. De Marzo, M.D., Ph.D. “Each needle sample takes 1/3,000 the weight of the prostate.” Twelve cores of tissue are 12/3,000 of the prostate, “and that is not a very good sampling, unless you have a very large tumor.”

What this means is that if your biopsy says you have “atypical cells,” that doesn’t mean you don’t also have cancer. If you have Gleason 3 + 3 cancer, that doesn’t mean you don’t also have some Gleason 3 + 4 cancer. If you have high-grade PIN, that doesn’t mean you don’t also have cancer.

It’s like “Let’s Make a Deal,” except there are many doors, and you don’t know what’s behind them. To sum up, the biopsy is the best guess, based on really small windows of insight.

Improving visibility: The good news is that there are many efforts to take out some of the guesswork.

The field is definitely changing,” says De Marzo. “Things are moving fast in every single realm of prostate cancer diagnosis.

New blood and urine tests can help determine if you have cancer, and if that cancer might be aggressive. Imaging is getting better, too. More men are getting prostate MRI, which can help show cancer – and can highlight suspicious areas for the urologist to target with the biopsy. is not widely available. Multi-parametric MRI looks at the prostate in four basic ways; each kind of imaging tells its own version of the story, and added together they give a more complete picture.

“Multi-parametric MRI requires a lot of expertise, and it has a learning curve,” says De Marzo. “Because the level of expertise varies, you should get this done at a center “that has a lot of experience with this type of imaging.” He adds, “I have great hope that as the field evolves, we will find a lot more and miss a lot fewer.”


Janet 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.