We have known for some time that women with dense breasts--higher amounts of epithelial and stromal tissue and less fat--have a higher risk for breast cancer. However, it has not been clear whether breast density was associated with specific types or characteristics of tumors--until now.

A new study conducted by the Harvard Medical School and Brigham and Women’s Hospital found that women with breasts that appear dense on mammograms are not only at higher risk of breast cancer, their tumors are more likely to have aggressive characteristics than women with less dense breasts.

The researchers compared breast density in 1,042 postmenopausal women with breast cancer with 1,794 matched control subjects who were similar in terms of age, postmenopausal hormone use, and other factors, but did not have breast cancer. They found that:

• The risk of breast cancer increased progressively with increasing breast density.
  • The associations were stronger for larger tumors than for smaller tumors; for high-grade than for low-grade tumors; and for estrogen receptor-negative than for estrogen receptor-positive tumors.
  • The link between density and breast cancer appeared to be stronger for ductal carcinoma in situ (DCIS) than for invasive tumors.
• There was no association between density and other markers of tumor aggressiveness, such as nodal involvement and HER2 status.

"Given that the magnitude of the association with breast density is strong across all breast cancer subtypes and particularly for ER-negative disease, breast density should be included in risk prediction models across tumor subtypes," they write.

These results are a wake-up call for all women with higher breast density to conduct regular breast self-exams and breast cancer screenings.

Source:

Journal of the National Cancer Institute