By Lisa Rapaport

(Reuters Health) – Women whose breasts are composed mainly of dense glandular tissue rather than fat may have higher odds of developing breast cancer, a recent study suggests.

Researchers examined data on more than 18,000 women with breast malignancies and 184,000 women the same age without breast cancer. They found breast density appeared to be the biggest indicator of cancer risk, even more than other common risk factors like family history or waiting until after age 30 to have babies.

“Women with dense breasts have a roughly 2-fold higher breast cancer risk relative to women with non-dense breasts,” said lead study author Dr. Natalie Engmann of the University of California, San Francisco.

This is a problem because 60 percent of younger women have dense breasts and so do 40 percent of older women who have gone through menopause – and because dense breasts make tumors harder to…