Dense Breast Tissue and Cancer Risks

Breast Density and How it Affects a Woman’s Risk for Breast Cancer

Consider the risk that an average woman will be diagnosed with breast cancer during the next 10 years of her life:

• Age 30: 0.44 percent (1 in 227)
• Age 40: 1.47 percent (1 in 68)
• Age 50: 2.38 percent (1 in 42)
• Age 60: 3.56 percent (1 in 28)
• Age 70: 3.82 percent (1 in 26)

The medical literature on the impact of density on this cancer risk is often misleading because most studies describe the risk by comparing the 10 percent of women in the highest density category (extremely dense) with the 10 percent of women in the lowest density category (almost entirely fatty). This is not meaningful to the other 80 percent of women, nor should risk comparisons be related to such a small subset of the patient population. When risk is expressed relative to average breast density (between scattered areas of fibroglandular density and heterogeneously dense), the risk for the 40 percent of women with heterogeneously dense breasts is only about 1.2 times greater and the risk for the 10 percent of women with extremely dense breasts is only about two times greater. Therefore, breast density is not a major cancer risk factor.