A new study says more women under 40 are being diagnosed with advanced breast cancer.

The number of American women ages 25 to 39 with advanced cases have climbed two percent every year since the 1970's.

Doctors say this is concerning because young women's tumors are likely to be more aggressive than older women's.

Younger woman are also less likely to have health insurance or get routine screenings.

The study is published in the Wednesday edition of the Journal of the American Medical Association.