Over the past 2-3 decades, an incredible amount of research has been done on breast cancer. One of the most important breakthroughs was discovering that most breast cancer is sensitive to estrogen. This has led to the development of medications that block estrogen. Your breast cancer pathology report will state whether your cancer is estrogen receptor-positive (ER+) or estrogen receptor-negative (ER-).
Breast cancer can also be sensitive to progesterone. This is also reported as progesterone receptor positive (PR+) or negative (PR-). This also factors into our treatment plan; however, it does not have as much impact as the estrogen receptor status.
Another critical tumor marker is referred to as HER2/NEU. This is reported as positive/amplified or negative/not amplified; HER2+ or HER2-.