# What is triple-negative breast cancer?

Source: https://oncologyistanbul.com/answers/what-is-triple-negative-breast-cancer
Last updated: 2026-07-13

According to the U.S. National Cancer Institute (NCI), triple-negative breast cancer (TNBC) is a type of breast cancer in which the tumor cells do not have estrogen receptors (ER-negative), progesterone receptors (PR-negative), or large amounts of HER2/neu protein (HER2-negative). Because those receptors and that protein are missing, the hormone therapy and HER2-targeted drugs used for other breast cancers have no target to act on and are not used to treat TNBC. NCI notes that it is often treated with chemotherapy, and that for some people the immunotherapy drug pembrolizumab may be given together with chemotherapy. This is general information, not personal medical advice; discuss your situation with your own care team.

## Verify at
- [NCI Dictionary of Cancer Terms — triple-negative breast cancer](https://www.cancer.gov/publications/dictionaries/cancer-terms/def/triple-negative-breast-cancer) — National Cancer Institute (NCI) (checked 2026-07-13)
- [Triple-negative Breast Cancer — Treatment](https://www.cancer.gov/types/breast/treatment/triple-negative-breast-cancer) — National Cancer Institute (NCI) (checked 2026-07-13)

Related: [What HER2-positive means](https://oncologyistanbul.com/answers/what-does-her2-positive-mean)