#BreastKeptSecret aims to help spread knowledge among women about the importance of knowing your breast density. Use this resource to get abreast of the latest information and help to ensure your friends and family are in the loop.

International clinical research shows women with high breast density (HBD) are at a greater risk of developing breast cancer, and also at a greater risk of breast cancer not being picked up by a mammogram.

Women with extremely dense breasts are 2 to 6 times more likely to develop breast cancer than those with extremely fatty breasts.

Breasts are made up of different types of tissue: fatty, fibrous and glandular. Fibrous and glandular tissue appear white on a mammogram as does cancer. Meanwhile fatty tissue shows up as dark. This means it is much harder to detect early stage breast cancer in dense breasts.

Breast density is not something you can feel through touch. It can only be picked up by a specialist doctor (most often a radiologist) on a breast screen e.g. a mammogram.

Once a woman has undergone a mammogram it is possible for the radiologist to “categorise” the breast tissue into one of four categories. The first two categories are less dense while the last two are the higher density groups. 

Women are encouraged to maintain a regular breast screening program. If you have high breast density speak with your doctor (GP or radiologist) about appropriate next steps, which may include additional screening (such as MRI/Ultrasound) and can have a cost associated with this. 


In Australia, these categories are defined in the following way:

  • Category 1. Predominantly Fatty Breast
  • Category 2. Scattered Fibroglandular Breast
  • Category 3. Heterogeneously Dense Breast
  • Category 4. Extremely Dense Breast

If you have any unusual symptoms, ask for a referral to a breast specialist or clinic even if your mammogram is normal.