ER/PR & HER2 Neu IHC Markers

Function

This panel measures Estrogen Receptor (ER), Progesterone Receptor (PR), and Human Epidermal Growth Factor Receptor 2 (HER2) status in breast cancer tissue using Immunohistochemistry (IHC). These markers are essential 'biomarkers' that determine how a tumor grows and how it can be most effectively treated.

Why it is Ordered

This test is mandatory for every new diagnosis of invasive breast cancer. It guides the oncology team in developing a personalized treatment plan:

• Hormone Receptor Status (ER/PR): Determines if the cancer cells grow in response to estrogen or progesterone. If positive, hormone-blocking therapies (like Tamoxifen) are effective.
• HER2 Status: Determines if the cancer overexpresses the HER2 protein. If positive (3+), targeted therapies like Trastuzumab (Herceptin) are used.

Associated Conditions

• Luminal A/B Breast Cancer: Usually ER/PR positive, indicating a generally better prognosis.
• HER2-Enriched Cancer: High HER2 expression; historically aggressive but now highly treatable with targeted biologics.
• Triple-Negative Breast Cancer (TNBC): Negative for ER, PR, and HER2. These are often more aggressive and require aggressive chemotherapy as they lack specific targets for hormonal or HER2-directed drugs.