Katie Couric was diagnosed with breast cancer after a mammogram. Don't skip your routine test

Katie Couric revealed she was diagnosed with breast cancer earlier this year, after a mammogram.

Couric shared in an essay published Wednesday on her Katie Couric Media website that, when she had a mammogram in June, her breast radiologist, Dr. Susan Drossman performed a biopsy. The next day, the doctor confirmed a cancer diagnosis.

Couric underwent surgery, followed by several sessions of radiation. In her essay, she urged people to get mammograms and find out if they may need additional screenings for breast cancer.

But what is a mammogram? At what age should you get a mammogram? Here’s what you need to know.

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What is a mammogram?

A mammogram is an X-ray image of a person’s breasts. Mammograms are typically used to look for signs of breast cancer, according to the U.S. Centers for Disease Control and Prevention. They can also be used to examine changes in a person’s breast, such as a new lump, pain in the breast, nipple thickening or discharge and more.

At what age should you get a mammogram?

The United States Preventive Services Task Force, a group of doctors and health experts who can make recommendations for medical professionals, says women who are 50 to 74 years old and are at average risk for breast cancer should get a mammogram every two years. Women between the ages of 40 and 49 should talk to their health care provider about when to start getting a mammogram and how often they should schedule one.

The American Cancer Society recommends that women ages 40 to 44 should have the choice to begin annual breast cancer screenings with mammograms, and women ages 45 to 54 should get mammograms every year.

Some women with genetic mutations may start screenings as early as age 25. Women with a family history of breast cancer can also screen starting "10 years earlier than the first affected relative in the family," according to the Cleveland Clinic.

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How does a mammogram work? Is it painful?

During a mammogram, a person’s breasts are compressed between “two firm surfaces to spread out the breast tissue,” according to the Mayo Clinic. An X-ray will then capture images that can be examined for signs of cancer or other health issues.

If a person has breast implants, they should still get regular mammograms, unless they had both breasts removed in a bilateral mastectomy, according to the American Cancer Society. The screening is also a little different - the breast is typically pulled out over the implant and the technologist will take more images, known as implant displacement views.

Some people do find a mammogram uncomfortable or painful, according to the CDC. Experts say people should try not to have a mammogram the week before or during their period, since a person’s breasts can be more tender during that time.

But regular mammograms “are the best tests doctors have to find breast cancer early, sometimes up to three years before it can be felt,” according to the CDC.

Do mammograms show cancer?

A radiologist examines a mammogram to look for any “high density regions or areas of unusual configuration that look different from normal tissue,” according to the National Institute of Biomedical Imaging and Bioengineering. Those areas could be cancerous tumors, but they could also be benign tumors, cysts and more.

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The radiologist will report the results to you and your doctor, and people typically hear the results within a few weeks, according to the CDC. If there is cause for concern, you may hear sooner.

How long do mammograms take?

Mammograms typically take less than 30 minutes, according to the Mayo Clinic.

If a mammogram shows any suspicious areas “that are not definitive for cancer, the radiologist may order additional mammogram views, with or without additional magnification or compression, or they may order a biopsy,” according to the National Institute of Biomedical Imaging and Bioengineering.

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What does it mean to have dense breasts? Does it affect your screening?

Couric appeared on "Today" with her former co-anchors Hoda Kotb and Savannah Guthrie on Oct. 3 where she discussed the importance of figuring out if you have dense breasts — which affects nearly 50 percent of women over 40, according to the National Cancer Institute. Dense breasts increase your risk of breast cancer and sometimes require additional screening.

"(Whether your breasts are dense) is not something you can tell by feeling your breasts, if your breasts are lumpy," Couric said. "You have to ask your radiologists, or your radiologist, ideally, should be telling you, 'You have dense breasts,' and then you often need secondary screening. So, my radiologist compared it to trying to find snowballs in a field of snow."

She added that the key to her doctor finding she had a tumor that needed biopsy was a breast ultrasound. Now, Couric is advocating for increased awareness and access to the procedure.

"All these breast cancers diagnoses would happen much earlier if, in fact, women with dense breasts had breasts ultrasounds," she said.

This article originally appeared on USA TODAY: Is a mammogram an X-ray for breast cancer? What age do you get one?