What Percentage of Abnormal Mammograms Are Cancer?

In some cases, especially when a sonomammography is done, noncancerous masses may show up as potentially cancerous lesions. Your doctor will need to do a biopsy to confirm if the suspicious mass is indeed cancer. The chance of having a false positive result after one mammogram is about 7%-12%. 

However, it’s important to be aware of the fact that if you have a false positive result, you may be at a slightly higher risk of developing cancer in the next 10 years. Rather than letting this terrify you, you can think of it as a heads up. Getting annual breast scans will help detect any future cancerous masses well before they spread in your body.

The diagnostic accuracy for mammograms increases for women over 50 years of age. That means that the older you get, the less likely it is that your mammogram will produce a false positive report. The technology used today can usually detect breast abnormalities before they can be felt during a breast exam.

While mammography is the best method available for early detection of breast cancer and more accurate than breast sonography, it’s not perfect. Below are some important statistics:

• About 7%-10% of women who have a screening mammogram are asked to come back for more testing (although only a small percentage of these women are later diagnosed with breast cancer).
• An estimated 17% of breast cancers may be missed by mammography. The number may rise as high as 30% for women with dense breasts, making the inclusion of a clinical breast exam in overall diagnosis even more important.
• Combining mammography with a clinical exam can diagnose about 4% more cancers than just mammography.

Regular mammograms can help detect breast cancer in the early stages. Mammograms also help diagnose some early precancerous conditions and early-stage cancers that appear as tiny calcifications (microcalcifications) on mammography, which are not detectable by physical examination. There are two types of mammograms.

• Screening mammogram: Usually performed annually in cases where there is no known problem.
• Diagnostic mammogram: Performed when there is a known problem that requires careful evaluation. Diagnostic mammograms provide much more extensive images than screening mammograms, such as views from additional angles and compression or blow-up views. Often an ultrasound and biopsy will be done in addition to the mammogram if there is a noticeable lump to confirm whether it is cancerous or aggressive.

One of the main reasons your doctor may recommend an ultrasound after a mammogram is if you have dense breast tissue. Dense breast tissue isn’t abnormal; however, it can make it more difficult for a mammogram to detect cancer cells that may be hidden in the tissue. 

An ultrasound can help provide a better diagnose after an abnormal mammogram because:

• A mammogram uses regular X-ray technology. Fatty tissue shows up as gray and dense tissue shows up as white. A cancerous tumor, however, also shows up as white.
• A breast ultrasound uses sound waves that bounce off tissue, with different tissues making different echo patterns. These patterns are studied to detect whether there are any cancer cells or abnormal tissue.
• While a mammogram shows a full picture of the breast and where the dense tissue is located, an ultrasound focuses on that dense tissue and shows what is inside it. It can therefore indicate whether there is a suspicious mass that needs to be confirmed through needle biopsy.

Apart from mammograms and ultrasounds, other diagnostic tests may be required to detect breast cancer along with clinical breast examination:

• Magnetic resonance imaging (MRI): Imaging of the breast is done using radio waves, magnetic fields, and computer imaging, offering a more detailed picture of the breast than a mammogram. This test is recommended for women with an above-average breast cancer risk due to certain factors such as family history or BRCA mutation.
• Nipple discharge exam: Fluid is collected from nipple discharge and then sent to the lab to look for cancer cells. Most nipple secretions are not cancerous and more likely to be caused by an injury, infection, or benign (noncancerous) tumor.
• Genetic screening: Women with elevated risk factors (such as a family history of breast cancer) may undergo genetic screening to see if they have mutations that put them at higher risk for developing the disease.
• Biopsy: Surgical removal of suspicious tissues for further examination. The type of biopsy done will depend on the location and size of the breast lump.

Currently, no diagnostic test other than a biopsy is 100% accurate. Since mammograms can cause false positive or false negative results, it’s important for women to be vigilant about regular self-examination, contact their doctors immediately if they notice anything unusual, and undergo annual testing to ensure early detection.