HER2 positive breast cancer is a type of breast cancer characterized by increased levels of the human epidermal growth factor receptor 2 protein or extra copies of the HER2 gene. This protein can promote cancer cell growth and division. Identifying HER2 status is an important part of diagnosis because it helps healthcare professionals determine appropriate treatment options.
HER2 positive breast cancer develops when cancer cells have higher-than-normal HER2 activity, which can encourage tumor growth. HER2 stands for human epidermal growth factor receptor 2, a protein involved in normal cell growth and repair. Although HER2 positive disease can sometimes grow more rapidly than certain other breast cancer types, advances in targeted treatments have improved outcomes for many patients. Treatment planning depends on factors such as tumor size, cancer stage, hormone receptor status, overall health, and whether the disease has spread to other parts of the body.
Diagnosing HER2 positive breast cancer generally begins with a clinical assessment when a breast change, screening result, or other finding raises concern. Symptoms may include a breast lump, changes in breast shape, skin dimpling, nipple changes, or discharge. However, some breast cancers are detected through screening before noticeable symptoms develop.
Imaging tests, including mammography, ultrasound, and sometimes magnetic resonance imaging, can help evaluate suspicious areas. A breast biopsy is usually needed to confirm cancer and examine the tissue. Pathologists assess the sample to identify the cancer type and determine its biological characteristics, including HER2 status.
Important diagnostic methods include:
Breast imaging: Mammography and ultrasound help identify and evaluate abnormal areas. MRI may be recommended in particular circumstances.
Biopsy: A tissue sample is examined to confirm the presence and type of cancer.
Immunohistochemistry testing: This test measures HER2 protein expression in cancer cells and commonly produces a score from 0 to 3+.
In situ hybridization testing: This method evaluates HER2 gene amplification and may help clarify results when immunohistochemistry is equivocal.
Hormone receptor testing: Estrogen and progesterone receptor results help determine whether hormone therapy may be appropriate.
HER2 results guide treatment selection. If results are uncertain or do not agree, additional testing or specialist review may be necessary. Patients should discuss their pathology reports with their healthcare team to understand the findings and their implications.
Treatment for HER2 positive breast cancer may involve several approaches used individually or in combination. The treatment plan depends on whether the cancer is early stage, locally advanced, or metastatic. Doctors also consider tumor characteristics, previous treatment, potential side effects, and the patient's preferences.
Common treatment approaches include:
Targeted therapy: Medicines such as trastuzumab and pertuzumab target HER2-related pathways and may be combined with other treatments depending on the disease stage.
Chemotherapy: These medicines destroy or inhibit rapidly dividing cancer cells and are often used with HER2-targeted treatment in appropriate cases.
Surgery: Breast-conserving surgery or mastectomy may be considered depending on tumor size, location, disease extent, and individual circumstances.
Radiation therapy: Radiation may be recommended after surgery or in other clinical situations to help control cancer in specific areas.
Antibody drug conjugates: Medicines such as trastuzumab emtansine and trastuzumab deruxtecan deliver cancer-targeting treatment and are used in selected settings.
Hormone therapy: If the cancer is also estrogen receptor positive or progesterone receptor positive, hormone therapy may form part of the treatment plan.
For some patients, targeted treatment begins before surgery to reduce the tumor and assess its response. Other patients receive treatment after surgery to lower the risk of recurrence. Metastatic disease may require ongoing systemic treatment, with medication choices influenced by previous therapies and the cancer's behavior.
Treatment can cause side effects, which vary by medicine and individual health. Some HER2-targeted therapies require monitoring of heart function. Chemotherapy may cause fatigue, nausea, hair loss, or changes in blood cell counts. Healthcare professionals can explain the expected benefits, risks, monitoring needs, and supportive care options.
Understanding HER2 status is central to selecting appropriate breast cancer treatment. Patients can ask their healthcare team how their test results, cancer stage, and hormone receptor status influence treatment recommendations. Regular follow-up helps assess treatment response, monitor side effects, and address changing care needs. Individual outcomes vary, so treatment decisions should be based on professional medical advice and the patient's specific circumstances.