PR+
Meaning of PR+: Mostly read as a second opinion on estrogen receptor status, since hormone treatment targets estrogen rather than progesterone.
Definition of PR+
PR+ means that testing has found progesterone receptors in a tissue sample, most often a breast cancer. Because the gene for this receptor is switched on by estrogen signaling, a positive result is usually read as a sign that the estrogen pathway in those cells is intact and working, rather than as proof that progesterone itself is driving growth.
How is the result produced?
The same stained slide that reports estrogen receptor status carries the progesterone result. An antibody binds the progesterone receptor in the nuclei of tumor cells, a stain makes it visible, and a pathologist reports the proportion of nuclei stained and the strength of that staining. The threshold for calling a sample positive is low, because tumors with modest levels still behave like positive ones. Controls run alongside the sample confirm the stain worked, since a technical failure would read as a negative result and change what follows.
What does a positive result add?
| Combination | What it suggests |
|---|---|
| ER positive and PR positive | An intact estrogen pathway; the most reliable response to endocrine treatment |
| ER positive and PR negative | Endocrine treatment still used, with less consistent benefit and a somewhat worse outlook |
| ER negative and PR positive | Uncommon; usually retested, since it often proves to be a technical result |
The value of a PR+ result therefore lies in the combination rather than on its own, which is why it is never reported in isolation from estrogen receptor positive or negative status.
What does it not mean?
A positive result does not mean that treatment blocking progesterone is used. Endocrine therapy in breast cancer acts on estrogen, by occupying the estrogen receptor, by lowering estrogen production or by degrading the receptor, and the progesterone receptor is measured for what it reveals about that pathway rather than as a target in its own right. Nor does the result predict, on its own, how fast a tumor grows or how far it has spread, since grade, stage and HER2 status carry that information. Read correctly, PR+ is one line in a hormone receptor profile, useful chiefly for the confidence it adds to the estrogen receptor result beside it.
Also known as
Used in a sentence
The tumor was reported as PR+ on receptor testing performed at the time of biopsy.
Good to know
PR+ status describes the presence of the receptor on laboratory testing and is distinct from estrogen receptor positive status, since a tumor can be positive for one receptor, both or neither.