ERPRpositive

ERPRpositive is a term used in oncology to describe a tumor that expresses both estrogen receptor (ER) and progesterone receptor (PR) proteins, most often in breast cancer. Expression is typically assessed by immunohistochemistry on tumor tissue and is reported as the percentage of tumor cell nuclei that stain positive, with an indication of staining intensity. A common threshold for positivity is at least 1% of tumor cells staining, though exact cutoffs can vary by assay and guideline. Tumors that are ER-positive and PR-positive are collectively called hormone receptor-positive and generally rely on estrogen signaling for growth.

Clinical implications include a higher likelihood of response to endocrine therapies that reduce estrogen activity. For premenopausal patients, tamoxifen is commonly used; for postmenopausal patients, aromatase inhibitors are typical, often with ovarian suppression in some cases. In advanced disease, combinations of endocrine therapy with targeted agents such as CDK4/6 inhibitors can improve outcomes. HR-positive status also informs prognosis, which is generally more favorable than hormone receptor-negative cancers, but late recurrences are possible.

Notes include that ER/PR status can differ between primary tumors and metastases, so re-testing of metastatic sites may be recommended. ER and PR are part of the broader category of hormone receptors, which may be present with any HER2 status. While ER/PR positivity predicts sensitivity to hormone therapy, resistance can occur and treatment plans may need adjustment over time.