Key Insights

• Understand how this test reveals your tumor’s hormone receptor status and what that means for endometrial cancer behavior and care planning.
• Pinpoint estrogen receptor (ER) and progesterone receptor (PR) expression in tumor tissue to explain growth patterns, grade, and likelihood of responding to hormonal therapy.
• Learn how tumor subtype and prior hormone exposure may influence receptor levels and shape your biological results.
• Use insights to guide personalized strategies with your clinician, including fertility-sparing approaches, endocrine therapy candidacy, and adjuvant treatment choices.
• Track how receptor status changes over time to understand recurrence biology and adjust your care strategy.
• Integrate ER/PR with related panels such as mismatch repair (MMR/MSI), p53, POLE, HER2, and proliferation markers for a more complete view of prognosis and treatment options.

What Is an ER/PR Test?

An ER/PR test measures how many cells in an endometrial cancer sample carry estrogen receptors (ER) and progesterone receptors (PR). It is performed on human tumor tissue collected during an endometrial biopsy, dilation and curettage, or surgery, and the specimen is processed in paraffin blocks for analysis. Pathology labs use immunohistochemistry, a staining method that tags specific proteins, so the pathologist can see and quantify receptor presence under a microscope. Results are typically reported as the percentage of tumor cell nuclei that stain positive and the intensity of that staining. Some labs also provide a composite score, such as an H-score, and classify results as positive or negative using lab-validated cutoffs.

This test matters because ER and PR are key switches that influence how endometrial cancer cells grow, differentiate, and respond to therapy. High PR, in particular, is often associated with more favorable biology and a greater chance of benefiting from hormonal (endocrine) treatment, while loss of ER or PR can be a sign of more aggressive behavior in certain subtypes. IHC-based receptor testing is a standard part of tumor profiling and helps translate complex cellular signaling into practical insights about prognosis and potential treatment pathways, though thresholds and scoring can vary by laboratory.

Why Is It Important to Test Your ER/PR?

In a healthy uterus, estrogen stimulates the endometrial lining to grow, and progesterone signals it to mature and stabilize. Endometrial cancers borrow these signaling pathways to different degrees. Testing ER and PR tells you whether the tumor is still “listening” to hormones. When receptors are present, cancer cells may rely on hormone-driven growth cues; when receptors are lost, tumors often behave differently and may align with higher-grade or non-endometrioid patterns. Measuring ER/PR helps reveal the biological drivers behind the tumor’s metabolism, cell cycling, and microenvironmental stress, which can link to inflammation, immune activity, and the likelihood of progression.

Clinically, ER/PR status supports prevention-minded decision making and fine-tunes treatment planning. For selected patients who wish to preserve fertility, strong PR expression can support the consideration of conservative, progestin-based management with close monitoring. In recurrent or advanced disease, ER/PR positivity can indicate that endocrine therapy may slow cell cycling by activating progesterone pathways that oppose estrogen-driven proliferation. On the other hand, low or absent PR may prompt earlier focus on non-hormonal options. In short, ER/PR testing does not label a simple pass or fail; it maps where your tumor stands along hormone-driven biology so your care team can match the strategy to the signal.

What Insights Will I Get From an ER/PR Test?

Your report usually displays ER and PR as percentages of tumor cells that stain positive, often paired with an intensity score or a combined index like an H-score. Laboratories apply validated cutoffs to determine whether a result is considered positive. “Normal” population ranges do not apply here because this is a tumor-specific assessment. Instead, you and your clinician interpret results relative to known patterns in endometrial cancer. The same numerical value can mean different things depending on tumor type, grade, and stage, so context is essential.

Lower percentages or complete loss of ER/PR may indicate that the tumor is less dependent on hormones and could be associated with more aggressive patterns in certain histologies. This does not, by itself, define stage or outcome. Rather, it prompts thoughtful integration with other findings. Many teams view ER/PR alongside MMR/MSI status, p53 abnormalities, POLE mutations, HER2 in serous tumors, and proliferation markers to refine prognosis and align the next steps.

The largest value of the ER/PR test is pattern recognition over time. If receptor testing is repeated at recurrence, a shift from positive to negative or vice versa can signal biologic evolution and shape therapeutic planning. Assay limitations exist, including differences in antibody clones, thresholds, and scoring systems across labs, as well as sampling variability within a tumor. That is why interpretation belongs in a clinical context that includes your pathology report, imaging, and overall health goals. Taken together, ER/PR status helps convert microscopic biology into clear, actionable insights for personalized care and long-term outcomes, even as ongoing research continues to sharpen the thresholds and use cases.