Dense Breast Screening: Where SpotitEarly's Breath-Based Approach Could Help

If you've recently been told that you have dense breast tissue, you're not alone. Nearly half of women undergoing routine mammograms have dense breasts, making it one of the most common findings reported during breast cancer screening. (NCI)

Dense breast tissue is not a disease, and it does not mean you have breast cancer. However, it can make breast cancer more difficult to detect by hiding tumors on a mammogram. It is also associated with an increased risk of developing cancer. In these situations having additional screening methods becomes important, including SpotitEarly's breath-based approach, designed to work regardless of how dense the breasts are. 

Although this article focuses on women, where breast density and mammography are most relevant, breast cancer is not exclusively a women's disease. About 1 in 100 breast cancers diagnosed occurs in a man, and because it is less expected, men are often diagnosed at a later stage (American Cancer Society).

What Is Dense Breast Tissue?

Breasts are made up of fatty tissue, fibrous tissue, and milk glands. When there is a greater proportion of fibrous and glandular tissue compared with fat, the breasts are considered dense.

Breast density cannot be determined by touch or physical examination. It can only be assessed on a mammogram, where fatty tissue appears dark (easy to see through) while dense tissue appears white (hard to see through). (NCI)

A radiologist assigns the density rating by comparing the amount of fatty tissue to fibrous and glandular tissue on the mammogram (NCI). The result is reported using one of four BI-RADS categories:

Source: National Cancer Institute

• A = Almost entirely fatty: very little dense tissue.

• B = Scattered areas of density: mostly fatty with some dense regions.

• C = Heterogeneously dense: largely dense tissue with some fatty areas.

• D = Extremely dense: nearly all dense tissue.

Women in categories C and D are considered to have dense breasts, and together these two groups account for roughly 40–50% of women who undergo screening mammography (U.S. Food and Drug Administration).

What Causes Breast Density?

Researchers don't fully understand why some women have more dense breast tissue than others. Several factors are associated with higher density (NCI):

• Are younger. Breast tissue tends to become less dense as you get older, though this doesn't happen to everyone, dense breasts can occur at any age.

• Have a lower body mass index. Less body fat makes it more likely that you'll have less fatty tissue and more dense tissue in your breasts.

• Take hormone therapy for menopause. Combination hormone therapy to relieve menopause symptoms makes dense breasts more likely.

Breast density often changes over time, varies from person to person, and can be influenced by factors such as body weight and hormone therapy. Each mammogram reassesses your current density (NCI). Since September 2024, the FDA has required mammography facilities to tell patients whether their breasts are dense and to encourage a conversation about additional screening (U.S. Food and Drug Administration).

Why Density Matters for Screening

Density affects screening in two ways.

First, it lowers the sensitivity of mammography: because both dense tissue and many cancers appear white, a small tumor can be hidden and missed.

Second, breast density is itself a risk factor. Women with extremely dense breasts (category D) have up to four times the risk of developing breast cancer compared with women whose breasts are almost entirely fatty (category A). About 10% of women fall into that highest-density group (The Lancet, 2025).

That makes routine screening especially important for people with dense or very dense breast tissue.

Screening Options for Dense Breasts

Mammography remains the foundation of breast cancer screening and should still be performed following the recommended guidelines. For patients with dense breasts and additional risk factors, additional options can be offered:

• 3D mammography (tomosynthesis): combines X-ray images from multiple angles.

• Breast ultrasound: uses sound waves to distinguish a solid mass from a fluid-filled cyst.

• Breast MRI: the most sensitive method, usually reserved for those at very high risk.

• Contrast-enhanced mammography: iodine-based contrast highlights areas of concern.

• Molecular breast imaging: a radioactive tracer read by a special camera (NCI).

A 2025 randomized trial offers the clearest comparison so far. Among more than 9,000 women with dense breasts and a negative mammogram, contrast-enhanced mammography detected 19 additional cancers per 1,000 women screened and abbreviated MRI 17, against the roughly 8 per 1,000 that mammography alone already finds (The Lancet, 2025).

Each has trade-offs: some find cancers a mammogram misses, but they can also raise false positives, and none has yet been proven to reduce breast cancer deaths in dense breasts specifically (USPSTF). The right mix depends on overall risk, not density alone.

Beyond Imaging

Other approaches skip imaging and look for cancer through different biological signals, useful in dense breasts, where tissue can hide a tumor. Most are complementary or still investigational:

• Risk factors to review with your provider: BRCA1 or BRCA2 gene mutations, family history of breast cancer, and previous breast biopsies.

• Clinical breast exam: palpation of the breast to check for a lump.

• Blood tests (liquid biopsy): read tumor DNA or proteins in blood (Nature Reviews Clinical Oncology).

• Breath analysis (VOCs): reads volatile compounds in exhaled breath.

Breath-Based Screening: SpotitEarly's Approach

SpotitEarly is developing a breath-based platform that pairs trained detection canines with AI, where a single at-home sample screens for breast and other cancers.

The approach has already shown promising results in the Rainbow Study — 1,386 participants, published in Scientific Reports — with 93.9% sensitivity and 94.3% specificity across multiple cancer types. For early-stage breast cancer (stage 0–2), sensitivity reached 93.8% (Scientific Reports, 2024).

Because a breath test reads exhaled molecules rather than breast anatomy, it isn't limited by density or by sex; in the Rainbow Study it performed comparably in men and women. For breast cancer detection, it is a density-independent option built to complement mammography, not replace it.