Progesterone Receptor

Every cell in the body contains proteins called receptors that bind to specific molecules — like a lock that only one key can open. A progesterone receptor is a protein inside cells that binds specifically to the hormone progesterone. When progesterone attaches to this receptor, it sends a signal to the cell that can affect how it grows and behaves.

In breast cancer pathology, testing for progesterone receptors is routine. If the tumor cells contain these receptors, the cancer is called PR-positive (PR+), meaning it may be using progesterone as a growth signal. If no progesterone receptors are present, the cancer is PR-negative (PR−). This result is almost always reported alongside the estrogen receptor (ER) status, because the two hormones are closely related in how they influence breast cancer behavior.

PR-positive breast cancers are generally considered hormone receptor-positive (HR+), which has significant treatment implications. These cancers are often eligible for hormone-blocking therapies — like tamoxifen or aromatase inhibitors — that work by reducing the amount of estrogen available or blocking its ability to bind to receptors. Knowing your receptor status is one of the most important pieces of information your oncologist uses to build your treatment plan.

Progesterone receptor status is one of the core pieces of information in a breast cancer diagnosis. It helps predict how a cancer is likely to behave and, more importantly, which therapies are most likely to work. PR-positive tumors tend to respond well to hormone-blocking treatments, which are generally well tolerated and have a long track record of effectiveness.

PR status is also one part of the broader molecular profile of a tumor that may be used to determine whether chemotherapy is necessary, or whether hormone therapy alone is sufficient. Tests like Oncotype DX use receptor status among other factors to generate an individualized risk and benefit assessment. Understanding your receptor status is empowering — it's a key that helps unlock the most personalized approach to your care.