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Understanding Breast Cancer and Mammograms

What if the radiologist sees something suspicious on your mammogram?

The fear this scenario evokes is real, but facts may help calm it. Most abnormalities on a mammogram are not breast cancer.

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On a screening mammogram, questionable abnormalities sometimes require additional evaluation. With further examination (imaging studies and/or biopsy), most of these abnormalities are found to be normal breast tissue or benign (non-cancerous) tissue.

What Is a Screening Mammogram?

The American Cancer Society recommends yearly screening mammograms starting at age 40. However, the U.S. Preventive Services Task Force (USPSTF) does not recommend screening for women in their 40s. For women between the ages of 50 and 74, USPSTF experts say women should have mammograms every two years and do not recommend screening at all after age 74.

When you need a mammogram is a personal decision between you and your doctor. If you're over 40, talk to you doctor about when you should begin mammogram screening.

In a screening mammogram, each breast is X-rayed in two different positions: from top to bottom and from side to side. When a mammogram image is viewed, breast tissue appears white and opaque and fatty tissue appears darker and translucent.

What if Something Looks Abnormal?

Potential abnormalities are found in up to 11% of women who have screening mammograms. This small group of women needs further evaluation that may include diagnostic mammography, breast ultrasound, or needle biopsy. Of those women asked to return for further testing, 20% to 50% will have breast cancer.

After the additional evaluation is complete, most of these women will be found to have nothing wrong.

What Is a Diagnostic Mammogram?

Diagnostic mammograms differ from screening mammograms in that the examination focuses specifically on an area of breast tissue that appeared abnormal in a screening mammogram. Diagnostic mammograms are also done for women who haven't had a screening mammogram but may be showing signs or symptoms of something abnormal in the breasts.

Depending on the potential abnormality, different studies may be done. In some women, only additional mammographic images are needed. In other women, additional mammographic images and an ultrasound are done.

How Does an Abnormality Appear on a Mammogram?

A potential abnormality on a mammogram may be called a nodule, mass, lump, density, or distortion.

  • A mass (lump) with a smooth, well-defined border is often benign. Ultrasound is needed to characterize the inside of a mass; if the mass contains fluid, it is called a cyst.
  • A mass (lump) that has an irregular border or a star-burst appearance (spiculated) may be cancerous; a biopsy is usually recommended.
  • Microcalcifications (small deposits of calcium) are another type of abnormality. They can be classified as benign, suspicious, or indeterminate. Depending on the appearance of the microcalcifications on the additional studies (magnification views), a biopsy may be recommended.

How Accurate Is Mammography?

Mammography is 85% to 95% accurate. Mammograms have improved the ability to detect breast abnormalities before they are large enough to be felt. Also, the accuracy of mammography improves as the patient ages.

However, it is possible for a mass to be felt but not appear on a mammogram. Because of this, your health care provider should evaluate any abnormality that you feel when examining your breasts. A diagnostic mammogram may be recommended.

A negative mammogram despite a lump you can feel does not rule out breast cancer. Mammograms will be falsely negative in up to 15% of patients. In these patients a biopsy is important.

WebMD Medical Reference

Reviewed by Sujana Movva, MD on October 25, 2012

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