context: HER2-positive breast cancer is a type of breast cancer in which breast cancer cells test positive for a protein receptor called human epidermal growth factor receptor 2. This protein's normal job is to help control how a healthy breast cell grows, divides, and repairs itself. But sometimes, something goes wrong in the gene that controls the HER2 protein (also called the ERBB2 gene) and your body creates too much of these receptors. As a result, your breast cells grow and divide uncontrollably. About 1 of 5 of breast cancers are HER2-positive. While HER2 is more aggressive than other types of breast tumors, there are treatments that can help. You'll work with your doctor to review the treatment options and come up with a plan that's best for you. The most common warning sign of any type of breast cancer is a lump in your breast that feels different from the area around it. That's true for the HER2-positive type, too. Other symptoms of HER2-positive breast cancer may include: Breast swelling A change in its shape Skin irritation or dimpling Pain in the breast or nipple Redness or thickness of the nipple or breast skin Discharge from the nipple (not breast milk) You may have noticed a difference in your breasts during a self-exam. Or you may have had a mammogram that showed a growth. Doctors don't know the exact causes of breast cancer. Experts think it may be a combination of things, including your genes, environment, and lifestyle. You can't inherit a bad copy of the HER2 gene from a parent, and you won't pass it on to your children. When you find out that you have breast cancer, your doctor will check to see if yours is HER2-positive. She'll probably give you one or more of these tests: The IHC test uses certain antibodies that identify the HER2 protein in a sample of breast cancer tissue. If there is a lot of it, the cells change color in the sample. The FISH test uses fluorescent pieces of DNA that stick to the HER2 gene in cells, which can then be counted under a microscope to see how many are in your cancer cells. The SPOT- Light HER2 CISH and the Inform HER2 Dual ISH tests use stains that color HER2 genes in a tissue sample so they can be counted under a microscope. Sometimes the results of a single test aren't clear. If that happens, your doctor may order another type. How are you sure my cancer is HER2-positive? Where exactly is my cancer? What stage is it? What are my treatment options? What treatment do you think will work best for me? How quickly do I need to start the treatment? How will the treatment make me feel? Is there a clinical trial I should consider? Will I be able to work? Do I need to have my breast removed? Do I need radiation? Do I need chemotherapy? Do I need hormone treatment? Will my insurance cover my treatment? What if my cancer doesn't respond to the treatment? Because your breast cancer is HER2-positive, your doctor will treat it a special way. This could involve: Chemotherapy: You might get it before surgery to shrink the tumor, after surgery to kill remaining cancer cells, as treatment for cancer that has spread, or combined with other medications. Radiation: You could get this treatment after surgery to lower the chances your cancer will return, or if your cancer has spread to other body parts. There are two main types: External beam radiation: A machine directs radiation to the area where the cancer was. Brachytherapy: Doctors use a device to put radioactive pellets inside your body for short periods of time. Surgery: For cancer stages I through III, your treatment will probably start with surgery. There are two main types: Lumpectomy or breast-conserving surgery: The surgeon removes just the tumor and some surrounding tissue. Mastectomy: Your entire breast is removed. You could also have surgery to check if the cancer has spread to nearby lymph nodes: Sentinel lymph node biopsy ( SLNB): The surgeon removes only the lymph node(s) under the arm to which the cancer would likely spread first. Axillary lymph node dissection ( ALND): The surgeon removes many (usually less than 20) lymph nodes from under the arm. Surgery may also be an option for stage IV, or metastatic, cancer to prevent or treat symptoms or complications. Targeted therapy: Doctors usually start HER2 treatment with special drugs called targeted therapies. They block HER2 receptors to help keep your cancer cells from growing. These drugs include: Lapatinib ( Tykerb), neratinib ( Nerlynx): Block certain proteins that can cause uncontrolled cell growth. Pertuzumab ( Perjeta), trastuzumab ( Herceptin): These stop cancer cells from receiving growth signals. T- DM1 or ado-trastuzumab emtansine ( Kadcyla). This combination medication was designed to deliver the chemotherapy medicine emtansine to HER2-positive cancer cells in a targeted way by attaching it to Herceptin. You may be on this treatment plan for a long time -- up to a year. It lowers the chances that your disease will come back. If you reach that point and your cancer hasn't gotten worse, your doctor may stop the chemotherapy but keep you on the targeted treatment. Hormone therapy: If your cancer is hormone receptor-positive, then you may also take drugs that stop the hormone estrogen from attaching to the cancer cells. There are two main types: Drugs that block estrogen receptors: Tamoxifen ( Nolvadex, Soltamox), toremifene ( Fareston), fulvestrant ( Faslodex) Drugs that lower estrogen levels (aromatase inhibitors, or AIs): Anastrozole ( Arimidex) Exemestane ( Aromasin) Letrozole ( Femara) Clinical trial: Ask your doctor if a clinical trial is a good option for you. These are studies that test treatments that aren't yet available to everyone to see how well they work and how safe they are. There are pros and cons -- you'll get regular medical care, and you might get an effective new treatment; but you could also be part of the group that gets a placebo -- no treatment at all. Or the treatment you get could have unpleasant side effects or just not work for you. Having breast cancer can be overwhelming. Remember, though: You're in control of your treatment decisions and how you live your life. These tips can help you stay healthy while you get treatment: Get the support you need, whether it's information about breast cancer, talking with someone, or practical help with daily tasks. It can all make a huge difference in how you feel. Listen to your body. Exercise can help you feel better, but only when you're up for it. Stay nourished. If you don't have much of an appetite, eat smaller meals every few hours, rather than three big meals. About 80% of breast cancers in the U. S. are what doctors call infiltrating. This means they break through the walls of the glands or ducts where they start and grow into surrounding breast tissue. Of those cancers, around 20% are HER2-positive. Many women do well with targeted treatments. Breast cancer of any kind is easier to treat when it's diagnosed early. If your disease spreads or comes back, there are still ways to treat it. The outlook for this type of cancer depends on things like the treatment you get and the stage of your cancer. But new treatments like chemotherapy plus trastuzumab have boosted survival rates: 7-year disease-free: Around 93% 10-year disease-free: About 70%-75% Overall: 80%-85% The American Cancer Society is a good starting place to find the support you and your family may need throughout your treatment and afterward. You may want to join a support group. That's a good way to meet people who know what you're going through, because they've been through it, too. Let your family and friends know how you're feeling. Tell them what they can do to help you. They may want to help but don't know what to do. Also, consider talking with a counselor. That could help you handle the emotions that can come with having cancer.