Researchers at the University of North Carolina at Chapel Hill and colleagues analyzed tumors using two basic approaches: first, using an unbiased and genome-wide approach, and second, within the context of four previously known molecular sub-types of breast cancer: HER2-enriched, Luminal A, Luminal B and Basal-like.
"Through the use of multiple different technologies, we were able to collect the most complete picture of breast cancer diversity ever," corresponding author Charles Perou of the University of North Carolina at Chapel Hill said in a statement.
"These studies have important implications for all breast cancer patients and confirm a large number of our previous findings. In particular, we now have a much better picture of the genetic causes of the most common form of breast cancer, namely Estrogen-Receptor positive/Luminal A disease."
Luminal A tumors were the main cause of U.S. breast cancer deaths -- accounting for approximately 40 percent, Perou said.
The study, published in the online edition of the journal Nature, also found a great similarity between Basal-like breast cancers and ovarian cancers.
"This study has now provided a near complete framework for the genetic causes of breast cancer, which will significantly impact clinical medicine in the coming years as these genetic markers are evaluated as possible markers of therapeutic responsiveness," Perou said.
Notable deaths of 2014 [PHOTOS]