Key Insights

• Understand how this test reveals your tumor’s hormone sensitivity—whether cancer cells display progesterone receptors that can influence growth and response to therapy.
• Identify a key biomarker that helps explain tumor behavior, refines prognosis, and clarifies which cancers are more likely to benefit from endocrine (hormone-blocking) treatment.
• Learn how genetic drivers and prior exposures—such as estrogen signaling, prior therapies, and tumor biology—shape your progesterone receptor status and what that means for care.
• Use insights to guide personalized prevention, treatment, or lifestyle strategies in partnership with your clinician, including planning systemic therapy choices and clinical trial discussions.
• Track how your results change over time to monitor response, recurrence, or evolution of the disease, especially if the cancer returns or spreads.
• When appropriate, integrate this test’s findings with ER, HER2, Ki‑67, and select genomic panels to build a more complete, guideline-aligned picture of your cancer.

What Is a Progesterone Receptor (PR) Test?

A progesterone receptor (PR) test measures whether breast cancer cells carry receptors—protein “locks” on the cell nucleus—that can be activated by the hormone progesterone. It is performed on tumor tissue from a biopsy or surgery (formalin-fixed, paraffin-embedded tissue). In the lab, pathologists use immunohistochemistry (IHC), a staining technique that tints PR-positive tumor cell nuclei. Results are quantified as the percentage of tumor cells that stain and the intensity of staining, often summarized as a percentage, an Allred score (0–8), or an H-score (0–300). Clinical guidelines typically define a tumor as PR-positive when at least 1% of invasive cancer cells show nuclear staining.

This matters because PR reflects how strongly a tumor is wired into hormone signaling pathways. Along with the estrogen receptor (ER), PR status helps map the biology driving growth and the likelihood of responding to endocrine therapy. It also adds prognostic information: PR-positive tumors, especially when ER is also positive, generally have more favorable outcomes. Testing provides objective data that can sharpen diagnosis, inform treatment selection, and highlight potential therapeutic targets long before symptoms or imaging alone can tell the full story.

Why Is It Important to Test Your Progesterone Receptor (PR)?

PR is a readout of hormone signaling inside breast cancer cells. When PR is present, it often signals an intact estrogen-PR pathway that fuels growth but can also be blocked by endocrine therapies. When PR is absent—especially in an ER-positive tumor—it may indicate a shift toward more aggressive biology, relative endocrine resistance, or alternative growth drivers. That makes PR testing especially relevant at initial diagnosis, after neoadjuvant therapy, and at recurrence or metastasis when biology can change. In short, PR helps translate the tumor’s internal “language” of receptors and signals into actionable clinical insight.

Stepping back, PR testing supports better prevention and outcomes by matching treatment intensity to tumor biology. Regularly reassessing receptors at key moments offers an early-warning system for change: a tumor that loses PR over time may respond differently to therapy; one that gains PR may become more hormone-sensitive. The goal is not to label you as “positive” or “negative” and stop there. It is to locate your tumor precisely on the map of hormone signaling so your care team can choose strategies that are more likely to work—and avoid those that are not.

What Insights Will I Get From a Progesterone Receptor (PR) Test?

Your report will show how many tumor cells are PR-positive and how strongly they stain, usually as a percentage with an intensity grade, an Allred score, or an H‑score. Laboratories compare these results to established cut points. According to major oncology guidelines, any staining in at least 1% of tumor nuclei is considered positive, while 1–10% is often described as “low positive,” which may carry less predictable benefit from endocrine therapy. “Normal” in cancer pathology simply means what is typical for the tumor type and stage, not a healthy baseline in the body. Context is essential: the same PR result can have different implications depending on ER, HER2, grade, and your treatment history.

When PR is robustly positive alongside ER, it suggests an estrogen-driven tumor with higher likelihood of responding to endocrine therapy and, on average, a more favorable prognosis. If PR is absent in an ER-positive tumor, it can signal relative endocrine resistance and a higher risk of recurrence—information that often guides treatment planning and follow-up intensity. PR status is also one of the anchors for classifying tumors into biologic subtypes that behave differently clinically.

Higher PR expression generally indicates stronger hormone signaling capacity in the tumor, while lower or absent PR can reflect alternative pathways driving growth. That does not equal disease progression on its own; rather, it cues your team to look more closely at complementary markers (ER, HER2, Ki‑67) and, when needed, genomic assays to refine risk and benefit estimates.

The real power of the progesterone receptor (PR) test is pattern recognition over time. Receptor profiles can shift with treatment or at metastasis, so retesting a new biopsy can reveal meaningful changes that alter therapy choices. Interpreted alongside your full pathology report and clinical picture, PR results help convert complex tumor biology into a clear, data-informed plan for the next step.