Breast Cancer That Develops Between Mammograms: What You Need to Know

How Common Is Interval Breast Cancer?

How Is Interval Breast Cancer Different?

“It's because interval breast cancer develops in a short time. It grows faster and through different mechanisms than the usual estrogen-dependent mechanisms,” says Monique Gary, DO, a breast surgeon and the medical director of the Grand View Health–Penn Cancer Network cancer program in Pennsylvania. “[IBCs] are more likely to be triple-negative or HER2 [human epidermal growth factor receptor 2] positive,” she says.

Treatment for IBC tends to include chemotherapy and radiation therapy. In some cases, more extensive surgery may be necessary. Anne Peled, MD, a breast cancer and reconstruction surgeon in San Francisco and co-director of the Breast Cancer Program at Sutter Health California Pacific Medical Center, says a key challenge with IBCs is determining if the cancer developed rapidly after a negative mammogram or if it was simply not detected on prior mammograms.

A Lump in the Breast May Be a Sign

Unlike breast cancer detected during regular mammogram screenings, which can be too small to feel, IBC is more likely to show up as a noticeable lump in the breast or underarm, Dr. Peled says. By the time physical symptoms appear, IBCs have often grown to a more advanced stage.

• Nipple discharge
• New nipple inversion or retraction
• Changes in breast appearance, such as dimpling, redness, swelling, or changes in breast size or symmetry

Who’s Most at Risk?

Other risk factors, Dr. Gary says, include:

• Breast Density Dense breast tissue can make tumors difficult to see on mammograms.
• Family History Having a family history of breast cancer increases your risk of IBC.
• Lifetime Risk A lifetime risk of breast cancer of more than 20 percent as assessed by a risk assessment tool raises your chance of getting IBC.
• Previous Breast Biopsies Having past breast biopsies that showed abnormal cells means you should be extra vigilant between mammograms.
• Multiple Breast Cancers A personal history of multiple previous breast cancers increases your risk of IBC.
• Genes Genetic mutations like BRCA1 or BRCA2 raise your overall breast cancer risk.

Advocate for Your Own Breast Health

You can stay a step ahead of interval breast cancer with these tips straight from experts.

Know Your Breasts

Interval breast cancers can develop rapidly between mammograms, so practice breast self-awareness. With breast self-awareness, you don’t have to follow a strict method or schedule. Instead, become familiar with how your breasts normally look and feel. “If we feel for ‘normal,’ when that ‘normal’ changes or when something happens outside of that ‘normal,’ your hands are going to know,” Gary explains.

According to Gary, how your breasts feel during the first, middle, and end of your menstrual cycle can vary. So, it’s important to get to know your breasts at different times.

Understand Your Family History

This includes whether anyone in your family has had breast or ovarian cancer. Sharing this information with your healthcare providers is crucial since family history significantly impacts your risk.

Being aware of your family history and whether you’re at higher risk for IBC can help to advance the detection faster, Gary says.

Find Out if You Have Dense Breasts

If your mammogram result letter notes you have dense breasts, discuss additional screening options, like magnetic resonance imaging (MRI) or ultrasound in addition to yearly mammograms, with your healthcare provider.

Use an Assessment Tool

There are tools available online, like the National Cancer Institute’s Breast Risk Assessment Tool, to calculate your lifetime risk of breast cancer. “In the U.S., if the lifetime risk of breast cancer using risk calculators (which take into account factors such as breast density and family history) is greater than 20 percent, the recommended screening plan is alternating MRIs and mammograms every six months,” Peled says.

Participate in Clinical Trials

Researchers are investigating how often women should be screened based on risk factors like family history, breast density, and genetic markers. Clinical trials, like the WISDOM Study, are for people who don’t have breast cancer, and when you participate, you play an important role in helping refine screening guidelines.

Know There’s Hope

IBC can be challenging, but new developments in screening, diagnosis, and treatment are always happening. These advances bring hope for better identifying those at risk and improving treatments for those diagnosed.

If, in between your annual mammograms, you notice any changes in your breasts, communicate your concerns with your doctor so you can catch a potential diagnosis as early as possible and get the care you need.

The Takeaway

About 1 out of 6 breast cancers will be an interval breast cancer, meaning it will show up between screening mammograms. Learning about your personal risk factors — such as dense breasts, family history, and genetic mutations — and staying vigilant about screenings can help ensure you are diagnosed as early as possible so you can receive prompt treatment. Even if you’ve had a normal screening mammogram less than a year ago, be sure to visit your doctor if you notice any concerning changes in your breasts.