World Dense Breast Day Date in the current year: September 25, 2024

World Dense Breast Day World Dense Breast Day is an annual awareness campaign held on the last Wednesday of September. It was launched in 2022 to educate the general public about dense breasts and highlight the importance of breast screening.

A human female breast consists of adipose tissue (fat) and a mammary gland that produces milk, held together by fibrous connective tissue. The density or firmness of the breast is determined by the fat-to-connective-tissue ratio; the less adipose tissue a woman has, the denser her breasts are.

There are four categories of breast density. Breasts in Category A consist mostly of fat tissue and have only a small amount of connective tissue. Breasts in Category B have scattered areas of dense tissue. Breasts in Category C (heterogeneously dense breasts) have large portions made of connective tissue, and breasts in Category D (extremely dense breasts) are almost entirely made of connective tissue.

Categories B and C are the most common; about 40% of women have Category B breasts, and approximately the same number of women have Category C breasts. About 10% of women have fatty breasts (Category A), and the remaining 10% have extremely dense breasts (Category D). Breasts in Categories A and B are not considered dense, and breasts in Categories C and D are considered dense. It should be noted that breast density can change over time.

Dense breasts are not a pathology; according to statistics, almost half of women over the age of 40 have dense breasts. While dense breasts are normal and common, they are considered a risk factor for breast cancer because cancers are more likely to grow in dense tissue than in adipose tissue. Another reason for concern is that dense breasts look white or gray on a mammogram, and so does breast cancer. Due to this, breast cancer is often diagnosed at a later stage in women who have dense breasts because dense breast tissue “masks” lumps.

So, what should you do if you have dense breasts? It is recommended that women with dense breasts and other cancer risk factor discuss the possibility of additional screening tests with a healthcare professional after taking a mammogram. Additional screening options include ultrasound, contrast-enhanced mammogram (CEM), MRI, and MBI (molecular breast imaging).

The World Dense Breast Day campaign was launched in 2022 by, an educational resource developed to provide information on breast density to both patients and healthcare professionals. The main purpose of the campaign is raise global awareness about dense breasts and ensure that women and health providers around the world have access to medically-sourced educational resources.

The inaugural social media campaign reached over 8.6 million people from 37 countries; more than 17,000 people interacted with the posts (clicked, liked or shared) in addition to seeing/reading them. The best way to join the campaign is to learn more about breast density and spread the word on social media using the hashtag #WorldDenseBreastDay. You can also wear a pink awareness ribbon to promote breast cancer awareness.

Remind me with Google Calendar


International Observances


World Dense Breast Day, international observances, awareness campaigns, dense breasts, breast density