The short answer
ER and PR status tell whether breast cancer cells have receptors for the hormones estrogen and progesterone. Positive results mean hormone therapy may help.
ER means estrogen receptor; PR means progesterone receptor.
These receptors are found on some breast cancer cells.
'Positive' means the cells have the receptors and may respond to hormone therapy.
'Negative' means the cells lack them, so hormone therapy is less likely to help.
Choose how you want to understand this
The full explanation.
What the letters mean
On a breast cancer report, ER stands for estrogen receptor and PR for progesterone receptor. Receptors are docking points on cells. When breast cancer cells carry these receptors, the hormones estrogen and progesterone can attach and encourage the cells to grow.
Positive versus negative
If the test is positive, the cells have the receptors, and the cancer may respond to hormone therapy — treatment that blocks or lowers those hormones. If it is negative, the cells lack the receptors, and hormone therapy is less likely to help.
Why it guides treatment
ER and PR status is one of the most useful pieces of a breast cancer report because it points directly to whether hormone therapy is a good option. Many breast cancers are hormone-receptor positive, which opens up effective treatment choices.
The bigger panel
ER and PR are usually tested along with HER2. When ER, PR, and HER2 are all negative, the cancer is called triple-negative and is treated with different approaches. Your report should list all three together.
Words to know
Tap any term to see what it means.
Common questions
▸What are ER and PR?
They are receptors — docking points — on some breast cancer cells for the hormones estrogen (ER) and progesterone (PR). Their presence affects how the cancer may be treated.
▸What does ER-positive mean?
It means the cancer cells have estrogen receptors, so estrogen can encourage them to grow. These cancers often respond to hormone therapy that blocks or lowers estrogen.
▸Is ER-positive or ER-negative better?
ER-positive cancers can be treated with hormone therapy, which is an advantage. Outlook depends on many factors, so no single result defines it.
▸How is this related to HER2 and triple-negative?
ER, PR, and HER2 are tested together. When all three are negative, the cancer is called triple-negative, which is treated differently.
How this page was created
Cancer Explained uses AI to organize and translate information from the authoritative sources cited on each page. Automated checks review claims, citations, clarity, duplication, and potential safety concerns before publication. Our content is not currently reviewed by physicians unless a specific qualified reviewer is named on the page. Cancer Explained provides general education and should not replace advice from your healthcare team.
Human medical review: not completed. At this time, most Cancer Explained content has not been reviewed by a physician or other healthcare professional. Pages with documented human medical review identify the reviewer, credentials, and review date directly.
Read more about our editorial process, our use of AI, and our corrections policy.
Spotted a problem? Report an error — a factual mistake, broken or outdated source, confusing wording, or anything that seems unsafe. Please do not include names, medical record numbers, dates of birth, addresses, or other identifying medical information in your report.
After using this page, do you understand what to do next?
Anonymous — we only record the answer, never who gave it.