A new study from Yale researchers finds black women are four times more likely to have a genetic mutation that makes breast cancer tumors deadly.

Black women are less likely than white women to get breast cancer. But the study says they are more likely to have aggressive tumors.

Experts have debated whether socio-economic status, diet or health care could be possible explanations for the different outcomes.

Assistant Yale professor Beth Jones says the study finds race alone is a clear factor in determining the likelihood that a tumor would be aggressive.

Jones and her colleagues collected patient data from 145 black women and 177 white women who had breast cancer.