Lab Testing for Breast Cancer

Decoding Breast Cancer Lab Tests: Hormone Receptors and HER2/neu

After a breast cancer diagnosis, your doctor may recommend lab tests to assess the tumor's characteristics and guide treatment decisions. Two common tests are the hormone receptor test and the HER2/neu test. Understanding these tests can empower you to participate actively in your treatment plan.

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Hormone Receptor Test

Hormone receptors are proteins found on or within cells that interact with hormones like estrogen and progesterone. These hormones can fuel the growth of certain breast cancers.

• Why it's done: The hormone receptor test helps determine if your tumor is hormone receptor-positive, meaning it relies on these hormones to grow. If so, hormone therapy, a treatment that blocks or reduces hormone levels, may be effective.
• Who needs it: This test is generally recommended for all types of breast cancer.
• How it's done: A sample of breast tissue, usually obtained through a biopsy, is analyzed in a lab. A special staining process called immunohistochemical staining (IHC) reveals the presence and quantity of hormone receptors.
• Results:
  • ER-positive (estrogen receptor-positive): The tumor has estrogen receptors.
  • PR-positive (progesterone receptor-positive): The tumor has progesterone receptors.
  • Hormone receptor-negative: The tumor lacks both estrogen and progesterone receptors.
• Implications: Hormone receptor-positive tumors often have a better prognosis and respond well to hormone therapy. The more receptors present, the greater the potential benefit from hormone therapy.

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HER2/neu Test

The HER2/neu test focuses on a gene called HER2, which produces HER2 proteins. These proteins regulate cell growth and division.

• Why it's done: About 25% of breast cancers have an overactive HER2 gene, leading to excessive HER2 protein production. This accelerates tumor growth and can influence treatment response.
• Who needs it: The HER2/neu test is usually recommended for invasive breast cancer and recurrent breast cancer.
• How it's done: Similar to the hormone receptor test, a tissue sample is examined in a lab. Several tests may be used, including IHC, FISH, SPoT-Light HER2 CISH, and Inform HER2 Dual ISH. These assess the amount of HER2 protein and the number of HER2 gene copies.
• Results:
  • HER2-positive: The tumor has an overactive HER2 gene and excessive HER2 protein.
  • HER2-negative: The tumor has normal HER2 gene activity and protein levels.
• Implications: HER2-positive tumors tend to be more aggressive, but they often respond well to targeted therapies that specifically inhibit HER2 activity.

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Blood Test for HER2/neu

In some cases, if there isn't enough tumor tissue for testing, a blood test called the serum HER2/neu test may be used. It measures HER2 protein levels in the blood, offering insights into treatment response and potential recurrence.

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Triple-Negative Breast Cancer

When a breast tumor tests negative for both hormone receptors (estrogen and progesterone) and HER2, it's classified as triple-negative breast cancer (TNBC). This subtype accounts for approximately 10-15% of all breast cancers.

• Characteristics: TNBC tends to be more aggressive and is more common in younger women, Black women, and those with BRCA1 mutations.
• Treatment Challenges:  Since TNBC lacks the receptors targeted by hormone therapy and HER2-targeted drugs, treatment options are more limited. Chemotherapy is often the primary treatment, and clinical trials may offer access to newer therapies.
• Prognosis: While TNBC can be more difficult to treat, advancements in research are leading to new treatment options and improved outcomes. It's crucial to work closely with your healthcare team to develop a personalized treatment plan.
• Support:  Organizations like the Triple Negative Breast Cancer Foundation offer valuable resources and support for individuals diagnosed with TNBC.

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Remember: Your healthcare team will interpret your test results and discuss the best treatment options for your specific situation. Don't hesitate to ask questions and seek clarification. Knowledge is power in the fight against breast cancer.

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