What is triple negative breast cancer?

Triple negative breast cancer (TNBC) is a rare cancer that affects about 13 in 100,000 women each year. It represents about 15 % of all invasive breast cancers. Triple negative breast cancer is one of three types of breast cancer. It is called as triple negative because it doesn’t have three markers associated with other types of breast cancer, which is important for prognosis and treatment. It’s one of the more challenging breast cancers to treat. But researchers are making steady progress toward more effective treatments. Overall, 77% of women who have triple negative breast cancer are alive five years after diagnosis. 

Source:  https://my.clevelandclinic.org/health/diseases/21756-triple-negative-breast-cancer-tnbc