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PROSTATE CANCER SCREENING AND DIAGNOSIS: WHY NEEDLE BIOPSIES AREN’T PERFECT

Posted under Men's Health-Erectile Dysfunction by admin

Despite these improvements, needle biopsy doesn’t always give definitive answers. Sometimes the needle misses the cancer; sometimes what’s under the microscope is almost impossible to label definitively as cancer.

Some cancers, particularly those developing in the peripheral zone of the prostate, spread laterally—like a thin sheet of plankton on the surface of the sea. So it’s not uncommon that the biopsy needle goes in too deep and overshoots the target area. That’s why, in an attempt to get a comprehensive picture, doctors also take several tiny samples from throughout the prostate in what’s called a sextant biopsy (six biopsies, one from the top, middle and bottom of the gland on the right and left sides).

“Breast or lung cancer makes a solid nodule, just like a fist, that you usually can detect by palpation or imaging,” says a Johns Hopkins pathologist who is an expert in diagnosing prostate cancer. But prostate cancer tends to infiltrate normal tissue, meandering around normal cells. Or, as another Johns Hopkins scientist explains, it spreads out like a hand, whose fingers flow into nearby tissue “like a river flooding a valley.” In these cases there can be a significant amount of cancer, but not in the form of a “convenient” lump that’s easy to feel or see on ultrasound.

Thus, it’s not uncommon for a needle biopsy to be negative—even though cancer is present. This is called a false negative, and it can give both the urologist

and the patient “a false optimism that the cancer isn’t there,” the pathologist continues. So, even if one biopsy is suspicious and a repeat biopsy is negative, “that doesn’t rule out that the first biopsy wasn’t cancer.”

Imagine the difficulty of trying to capture this elusive tissue in a biopsy, using only a tiny needle. In some cases, it’s like looking with a needle in a haystack. The thin needles used for most prostate biopsies capture tiny cores of tissue—each about a millimeter thick—which pathologists then study under the microscope.