Triple-negative breast cancers are more likely than other breast cancer types to metastasize and are especially likely to go the brain in younger women. Researchers have tested various hypotheses to explain this danger. One idea that has gotten little attention is the thought that estrogen might be to blame. After all, triple negative breast cancers lack estrogen receptors (along with progesterone receptors and HER2, thus the name triple negative), and so these cancers can’t possibly be influenced by estrogen. Right?