HER2 Testing in Ductal Carcinoma In Situ: What You Need to Know - Breast and Thyroid

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Understanding HER2 Testing in Ductal Carcinoma In Situ (DCIS) is crucial for patients navigating their breast cancer diagnosis and treatment options. In your case, you have been diagnosed with DCIS, and your pathology report indicates positive estrogen receptor (ER) and progesterone receptor (PR) status. However, HER2 and Ki-67 were not tested, and your physician mentioned that HER2 testing is not necessary for DCIS because it does not typically influence treatment decisions.


Why HER2 Testing is Typically Not Performed in DCIS
Ductal Carcinoma In Situ is a non-invasive form of breast cancer where abnormal cells are found in the lining of a breast duct but have not spread beyond that duct. The primary treatment for DCIS usually involves surgery (lumpectomy or mastectomy) and possibly radiation therapy. Hormonal therapy may be considered based on ER and PR status, but the role of HER2 in DCIS is less clear compared to invasive breast cancer.

HER2 (human epidermal growth factor receptor 2) is a protein that can promote the growth of cancer cells. In invasive breast cancer, HER2 status is critical because it helps determine the use of targeted therapies like trastuzumab (Herceptin). However, in the case of DCIS, the clinical implications of HER2 status are not as significant, primarily because the treatment does not typically involve HER2-targeted therapies. Therefore, many oncologists may choose not to test for HER2 in cases of DCIS.


The Role of Ki-67 in DCIS
Ki-67 is a marker used to determine the proliferation rate of cancer cells. While it can provide information about the aggressiveness of a tumor, its role in DCIS is still being studied. High Ki-67 levels in invasive breast cancer can indicate a higher risk of recurrence, but the same correlation in DCIS is not as well established. Consequently, some physicians may not routinely test for Ki-67 in DCIS cases.


Should You Request HER2 and Ki-67 Testing?
If you are concerned about your HER2 and Ki-67 status, it is entirely reasonable to discuss this with your healthcare provider. You have the right to request additional testing if you believe it could provide you with more information about your cancer and potential treatment options. While your physician may have valid reasons for not recommending these tests, expressing your concerns and desire for more information is important.

The Importance of Communication with Your Healthcare Team
Open communication with your healthcare team is essential. If you feel uncertain about the implications of your diagnosis or the rationale behind the testing decisions, do not hesitate to ask questions. You might inquire about:
1. The rationale for not testing HER2 and Ki-67: Understanding your physician's perspective can help clarify why these tests may not be deemed necessary.

2. Potential benefits of knowing your HER2 and Ki-67 status: Discuss how this information might influence your treatment plan or follow-up care.

3. Options for additional testing: If you wish to pursue testing, ask about the process and any potential costs involved.


Conclusion
In summary, while HER2 testing is not routinely performed in cases of DCIS due to the lack of targeted therapies for this non-invasive cancer, it is your right as a patient to seek further information. Engaging in a dialogue with your healthcare provider about your concerns and preferences is crucial for your peace of mind and informed decision-making regarding your health. Remember, understanding your cancer and treatment options empowers you to take an active role in your care.