Scientists working with the government have looked at the DNA of breast cancer tumors from more than 900 women.
Although doctors have broken down breast cancer into 4 basic genetic types, they wanted to go deeper, to get a more detailed map of the genetics which drive tumors.
In the end, they found hundreds of genetic mutations - minute differences in the tumors, even on genes they thought they already understood. It's led them to break down one of the 4 breast cancer categories into two subgroups.
Dr.Brian Czerniecki, of the Abramson Cancer Center at the University of Pennsylvania, says those differences give researchers a better idea how to fight cancer, with a more personalized, effective treatment.
"You can map their tumor, they can do a gene analysis and say - well this person would be better off with getting these 3 components, as opposed to everybody getting just one," says Dr. Czerniecki.
The study also revealed some breast cancers have the same biological makeup of tumors found elsewhere, such as in the ovary.
So Dr. Czerniecki says in the future we may call cancers by their genetic makeup instead of where they start.
It also means some drugs already working for one type of cancer can work elsewhere in the body.
Before those can be used for new purposes, they will have to be tested for effectiveness and side effects.
Dr. Richard Besser, ABC's Chief Health and Medical Editor, says, " Certain breast cancers are much more like ovarian cancer and that may lead some doctors to treat those breast cancers with other drugs."
Still, some cancer experts don't think new research will change treatment much in the short term, since there is already a trend toward more tailored treatments. But many believe it could speed up the pace for new medications.
"As long as the FDA can keep up with the pace, I think you'll see the pace will be astronomical for the next 10 years," says Dr. Czerniecki.