Whew! If you’ve ever had a mammogram, you know that feeling of relief when that letter arrives in the mail saying your results are ‘normal.’ Most women exhale and then toss the letter in the garbage. But we ask, hold on! You need to do one more thing for yourself: find out your breast density.

What most women do not know is that a ‘normal’ mammogram result may not be accurate, especially if you have dense breasts. If you have fatty breasts, you can rest assured: mammograms are about 98% accurate in picking up breast cancer. However, if you have dense breasts, the accuracy in detecting cancer can be less than 50%. It is shocking that women are not told this.

The number one reason for breast cancer being missed in mammography is dense breast tissue. Ask a breast imaging radiologist and they will admit how difficult it is to see cancer in mammograms of women with dense breasts. The reason is that dense breast tissue appears white on a mammogram and so does cancer, thereby creating a camouflaging effect. “It’s like finding a polar bear in a blizzard” or “a snowball in a snowstorm.” For women with dense breasts, mammograms are simply not enough. If you have dense breasts, you may benefit from ultrasound, which finds additional cancers missed by mammography in dense breasts.

In addition to the camouflaging effect on mammogram, dense breasts are an independent risk factor for breast cancer, making cancer 4-6 times more likely in women with the highest density. Dense breasts are a more significant risk factor than having a family history of breast cancer. Women with dense breasts are 18 times more likely to have an interval cancer, where a lump is discovered after having had a normal mammogram.

Women with dense breasts need to know their density so that they can be aware of the risks. They should also have the option to consider additional screening, such as ultrasound. Early detection is the key to less aggressive treatment and increased survival rates. Please be your own breast health advocate and then spread the word: knowing and understanding your breast density matters. Check out how you can find out your breast density in your province by clicking here to go to our home page listings.