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Identifies a nuclear hormone receptor regulated by estrogen receptor (ER) activity and used as a marker of an intact ER pathway. Progesterone receptor (PR) is expressed in 60–70% of invasive breast cancers and provides additional predictive value alongside ER for determining response to endocrine therapies, including tamoxifen, SERMs, and aromatase inhibitors. Its primary clinical use is to help predict benefit from hormonal treatment in both early-stage and metastatic breast cancer.
Tissue Block: Formalin-fixed, paraffin-embedded (FFPE) tumor block preferred.
Unstained Slides: Recommended 2 charged slides per stain requested (minimum of 1 slide per stain), baked or unbaked.
Fixation: Tissue must be fixed in 10% neutral buffered formalin for 6–72 hours.
Use cold pack for transport. Make sure cold pack is not in direct contact with specimen.