To fight a disease, you have to know how it starts. Researchers now say they've found which genes' mutations lead to breast cancer.
An international team says out of the 20,000 possible genes, or genetic instructions, 93 can turn a normal breast cell cancerous if mutated.
The leader of the new study told the BBC that universities and pharmaceutical and biotech companies can now take that list and develop drugs that work for specific genes' mutations.
But there's also a downside: 60 percent of mutations in the breast cancer cases studied were found in just 10 genes.
That means there will likely be a much smaller financial incentive to develop drugs for the 83 other genes and their mutations.
Still, the researchers say the discovery is a big step forward for personalized medicine.
With current, more generic breast cancer treatments, more than 70 percent of people in the first three stages of the disease survive at least five years. But once it progresses to the most severe stage, only 22 percent of people survive that long.