HER2-positive breast cancer cells make too much of a protein receptor that helps grow and repair itself. These cancers respond better to targeted treatments directly targeting the HER2 gene product. If a mammogram suggests possible cancer, you may need a biopsy to test for it. Doctors perform core needle or surgical biopsies to remove tissue for testing.
Your prognosis depends on many factors, including the cancer stage and treatment response. In the past, HER2+ breast cancer was more likely to increase and spread (metastasize) or come back after treatment than breast cancer that did not overexpress HER2. However, recent drug therapy advances have improved the outlook for people with HER2-positive cancers. About one in five invasive breast cancers is HER2-positive. Your doctor tests HER2 status by running an immunohistochemistry test on tumor cells removed during surgery or biopsy. The test measures the amount of HER2 protein in the cells and gives a score from zero to three. A score of two is equivocal, and doctors will conduct more testing with a unique pathology technique called fluorescence in situ hybridization (FISH) or with a different tissue sample to clarify the HER2 status. If HER2-positive breast cancer is hormone sensitive, it may be treated with estrogen and progesterone drugs alone after surgery. But if it is metastatic, your doctor will likely treat you with chemotherapy plus HER2-targeted therapy for up to a year. Some people with HER2-positive cancers who are not hormone-sensitive benefit from a targeted therapy, which works by blocking the HER2 protein. Other patients with HER2-positive metastatic breast cancer may be candidates for clinical trials of a new vaccine to help stimulate the immune system and fight cancer.
Stage of Cancer
A breast cancer diagnosis can be terrifying, especially if your doctor explains that the prognosis is affected by the stage of the tumor. The staging system describes how much cancer is present in a particular body area and whether it has spread (metastasized) at the time of diagnosis. The staging is determined by what the doctor finds during the examination, tests, and biopsies. Staging systems are complex and might be hard to understand at first. Your doctor should explain your prognosis in a way that makes sense to you, so ask questions if you need help understanding. The cancer stage mainly depends on the tumor size and whether it is hormone receptor-positive or HER2-positive. Hormone receptor-positive tumors have ERs or PRs and are usually less aggressive than hormone receptor-negative tumors, but they can still recur years after treatment has ended. HER2-positive tumors have too many HER2 proteins on their surface and are more likely to grow and spread than HER2-negative tumors. Your doctor will determine if your tumor is HER2 positive by doing a biopsy and sending a tissue sample for testing. The doctor will use a test called immunohistochemistry or fluorescence in situ hybridization to check for the HER2 protein. If you have a HER2-positive tumor, your doctors might recommend a specific treatment, including chemotherapy and monoclonal antibodies that stick to the HER2 proteins to slow cancer cell growth.
When a doctor suspects breast cancer, it’s essential to get a mammogram to determine the size of the tumor and whether it has spread. If the mammogram indicates that there may be a suspicious area or growth, you might undergo a biopsy to test for cancerous tissue. The standard procedure is a core needle biopsy, in which a sample of the suspected cancerous tissue is taken from the breast with a needle. Your doctor might perform a surgical biopsy if the tumor is too large for a core needle biopsy. Once the biopsy is complete, your doctors will use IHC to test for HER2 status. Your treatment depends on your stage and HER2 status at diagnosis. You might not need chemotherapy if your tumor is in the earlier stages (stages 0 or 1) and is HER2-negative. You will likely receive chemotherapy if your HER2-positive cancer is in the later stages. You might receive other medications that target the HER2 protein. Some of these drugs, called antibody-drug conjugates, combine a monoclonal antibody with a chemotherapy drug, and others block signals that trigger uncontrolled cell growth.
Some breast cancers make extra HER2 (human epidermal growth factor receptor 2), stimulating cancer cells to grow. About one in five invasive breast cancers is HER2-positive and tends to affect younger women. HER2-positive cancers are more likely to be aggressive, but advances in treatment are improving the outlook for this type of cancer. Doctors can check whether a person’s breast cancer is HER2-positive by evaluating tissue from a biopsy. Core needle biopsies, in which a tissue sample is removed with a needle, and surgical biopsies are the most common types of breast biopsy. Some doctors may also use sentinel node biopsy to check for HER2 status. This involves injecting a dye or a radioactive tracer into the breast and examining the first lymph nodes under the arm that cancer might spread to. A HER2 test is done in a hospital laboratory on a breast cancer tissue sample taken from the patient through a biopsy or surgery. Doctors usually report the results as a score of 0-3, with 3+ meaning the cancer is HER2-positive. A HER2 test can sometimes come back with a borderline score (2+), in which doctors might want to retest the tumor using more specialized techniques. People with HER2-positive breast cancer can be treated with medications that prevent the cancer from growing or spreading, even when the tumor has already reached other body parts. These medications can lower a person’s risk of cancer recurrence and help them live longer.