Breast Density and Risk

Question: How high is the cancer risk associated with breast density?

Answer: 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% (1 in 227)
  • Age 40: 1.47% (1 in 68)
  • Age 50: 2.38% (1 in 42)
  • Age 60: 3.56% (1 in 28)
  • Age 70: 3.82 % (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% of women in the highest density category (extremely dense) with the 10% of women in the lowest density category (almost entirely fatty). This is not meaningful to the other 80% 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% of women with heterogeneously dense breasts is only about 1.2 times greater and the risk for the 10% of women with extremely dense breasts is only about 2 times greater. Therefore, breast density is not a major cancer risk factor.