Interval breast cancer is a malignancy in the breast diagnosed between the time of a negative screening mammogram and the next scheduled screening. These cancers appear after being told a screening was clear. They usually present as a new lump (or other symptoms) before a patient's next routine appointment.
Interval breast cancers are often more aggressive and advanced since they appear between routine screenings. This type of breast cancer may be associated with breast density, specifically denser breast tissue. Other factors include a family history of breast cancer risk and aging breast tissue.
Below, we’ll walk through what interval breast cancer is, how it relates to dense breast tissue, and how you can be more proactive about your breast health.
Current Breast Cancer Screening Guidelines
Breast cancer screenings are an important tool in the fight against cancer, but guidelines vary. They’re personalized based on your age, breast tissue density, and risk level (average or high).
According to the American Cancer Society, the guidelines for women of average risk are as follows:
- Ages 40 to 44 - Annual mammogram screening is optional
- Ages 45 to 54 - Annual mammograms are recommended
- Ages 55 and older - Women can choose between annual mammograms or having one every other year
Women with dense breasts are generally advised to begin screening at age 40 as well. Those at higher risk of breast cancer should talk with their doctors about starting mammograms earlier and whether more intensive imaging—such as breast ultrasound—is appropriate.
Adding a breast ultrasound screening to your routine is a proactive way to support early detection—especially for catching cancers that can develop in between mammograms. For women at higher risk, this might look like adding an ultrasound around six months after a mammogram, as part of a more frequent screening plan. HerScan helps make this kind of screening easier to access through community-based events—no doctor’s order or referral required—so more women can do something for their breast health instead of waiting for the next annual exam.
Is Interval Breast Cancer More Dangerous Than Other Cancers?
Interval breast cancer is considered more dangerous than screening-detected breast cancer for several reasons. Interval cancers are much more likely to be found once they are already at Grade 3. Once identified, it is often advanced and more aggressive at a later stage.
Although interval breast cancers are associated with poorer outcomes, newer screening technologies may help reduce these risks over time. Understanding your individual risk factors is key to creating a better screening approach. It’s also important to stay familiar with the signs and symptoms of breast cancer so you can quickly recognize any changes.
Dense Breast Tissue May Hide Cancers
Dense breast tissue may hide cancer on a mammogram because tissue and tumors both appear white. This makes tumors difficult to detect. If your breast tissue ranks as a category C or D, then additional screening tests, such as breast ultrasound, are recommended alongside your annual mammogram. Furthermore, research shows that undergoing breast ultrasound and MRI imaging may offer a better rate of detection.
Dense breast tissue does not turn into cancer. However, women with more breast density are at a higher risk of developing breast cancer than women without dense breast tissue.
False Negatives and "Normal" Results
Breast cancer screenings are highly effective at reducing the rate of breast cancer mortality. When cancer is caught early, there is a 99% survival rate for five years or more. However, this percentage drops to 33% if it spreads.
When a mammogram screening misses breast cancer present during the time of screening, this is called a "false negative." False negatives happen for many reasons, including breast density. Another reason is that some types of cancer grow in thin sheets instead of round lumps. This makes them nearly invisible on standard mammogram imaging. While an imaging result may appear normal, breast cancer could be present, but too small or subtle to detect (at that time).
How Common Is Interval Breast Cancer?
Interval breast cancer is common. Research shows that interval breast cancer accounts for between 20% to 30% of all breast cancer diagnoses in women who receive regular screenings. This varies depending on your breast density, age, length of time between screenings and if other screenings are used.
Screen-detected cancers are often found when they are microscopic. But interval cancers are almost entirely diagnosed because a patient noticed physical changes that caused them concern. Some of the most common changes include:
- The appearance of a new lump
- Dimpling, redness, puckering or changes to the breast skin's texture
- Nipple abnormalities (inversion, pulling to one side or scaling of the skin)
- Unusual discharge from the nipple that's not breast milk
Additional symptoms include painful or burning sensations or the sudden growth of one breast.
How To Be Proactive About Breast Health
Even though interval cancers are often more advanced, there are still important steps you can take to be proactive about your breast health:
- Know your breast density. This can help you better understand your individual risk.
- Follow through on recommended screenings. If your doctor recommends additional imaging, such as ultrasound, make it a priority.
- Don’t wait on new symptoms. If you notice changes in your breasts, don’t wait until your next scheduled screening—contact your provider promptly.
Women should continue to receive regular mammogram screenings, even though mammograms may not detect every type of cancer. Mammograms can still identify subtle changes, such as tissue being pulled or distorted by a cancerous mass, and can detect microcalcifications, which may be early indicators of breast cancer.
Why HerScan for Breast Cancer Screening?
HerScan is proud to help women do more for their breast health. With our mobile breast ultrasound screening services, we provide easy access to testing by using state-of-the-art ultrasound technology. Our credentialed technologists have extensive experience in breast imaging protocol and can provide you with a quick and convenient screening at a time that works best for you. Your results will be securely delivered to you to share with your provider, so you can take the next best steps for your breast health.
