There’s no getting around it: Biopsies can be scary. They’re usually done to confirm (or rule out) the presence of cancer or other serious diseases. That’s why it pays to know as much as you can about biopsies.

Six common myths about biopsies—and the facts you need to know…

MYTH #1: Biopsies cause cancer to spread. Many people worry that disturbing a tumor with a needle or surgery to perform a biopsy will allow cancer cells to “escape.”

Recent research: Studies have dispelled this common belief. In one recent study of pancreatic cancer patients, those who received a biopsy had better outcomes and lived longer than those who did not have a biopsy.

Possible exceptions: Surgeons have long recognized that a testicular biopsy can potentially cause “local spread” through blood and lymph vessels. Because of this, testicular tumors that appear to be malignant on imaging tests are usually tested (and treated) by removing the entire testicle.

Ovarian tumors that appear likely to be malignant on imaging tests (and contain some fluid) also are not biopsied because leakage of the fluid could cause malignant cells to spread. Cancer surgeons are aware of such exceptions.

MYTH #2: Biopsies are used only for cancer diagnosis. There are many types of biopsies. They include fine-needle aspiration (a needle is used to withdraw material—often fluid—from a mass)…core biopsy (a hollow needle is used to remove narrow cylinders of suspicious tissue)…and incisional biopsy (part of the tumor is removed surgically). All involve removing small amounts of tissue that will be analyzed in a laboratory.

It’s true that a biopsy will usually answer an important question—Do I have cancer? Your doctor will order this test if he/she suspects that you have cancer—based on symptoms, a physical exam (such as a breast or prostate exam), laboratory tests or a finding on an X-ray or a computed tomography (CT) or MRI scan.

But diagnosing cancer is not the only reason that a person might have a biopsy. Biopsies are used to diagnose many other diseases, such as celiac disease and hepatitis.

MYTH #3: Bigger is better. It makes intuitive sense that a big biopsy—one that removes a lot of tissue or even an entire tumor—is always more accurate than one that removes just a smidgen of tissue.

This might have been true in the past, but not now. Smaller biopsies usually cause fewer complications, and patients recover faster. Surgeons often don’t need to remove a lot of tissue to diagnose cancer because lab tests have become more sophisticated. Newer technology, such as image-guided biopsy, allows doctors to aim needles with pinpoint accuracy with the aid of an ultrasound or other imaging procedure. Most breast and prostate cancers can be diagnosed with core-needle biopsies, and most lung and colon cancers are diagnosed by endoscopic biopsies (taken with small instruments operated through a narrow, flexible, lighted tube).

MYTH #4: One tissue sample is enough. Suppose that a man with a small prostate cancer is given one core biopsy. If the sample doesn’t contain cancer cells, the man would be declared cancer-free (a “false-negative”). Surgeons are aware of this risk and take measures to prevent it. In the past, for example, a urologist would usually take six core samples from the prostate gland. Now it’s routine to take twice that many, making it less likely that cancer cells will be missed.

It’s still possible for a small cancer to “hide” from a biopsy or for a cancer not to be recognized by testing in the lab. With this possibility in mind, even if an initial biopsy is declared benign, a patient who appears to have cancer will get a closer look as well as possible follow-up testing and exams.

MYTH #5: Biopsies are definitive. Most pathologists looking at the same tissue samples will come to the same conclusion—but it’s not 100%.

Pathology is still the best way to diagnose and classify cancer, but it isn’t quite as exact as most people imagine. Interpretations are made by humans—and humans have differing opinions (and occasionally make mistakes). The difference between benign and malignant cells isn’t always clear-cut.

My advice: Get a second pathology opinion if the report does not jibe with the opinions of your doctor and/or radiologist. Your oncologist should be able to recommend a pathologist for a second opinion, which is usually covered by health insurance.

MYTH #6: Cancer cannot be detected without a tissue sample. Many kinds of cancer can be diagnosed by cytology—samples of cells that are in urine or sputum or gently scraped from the surface of organs (like Pap tests of the cervix). Radiologists can be confident enough about the appearance of some tumors on X-rays and scans that a biopsy is not needed. For example, most kidney tumors can be diagnosed from an imaging test.

On the horizon: “Liquid biopsies,” in which doctors look for circulating tumor cells, DNA or other substances in blood samples. This approach may soon be used to monitor how well patients respond to chemotherapy or other treatments. In the future, it might replace some biopsies for diagnosing cancer—but the technology isn’t there yet.