Cancer starts when cells change and grow out of control. The changed (abnormal) cells often grow to form a lump or mass called a tumor. Cancer cells can also grow into (invade) nearby areas. And they can spread to other parts of the body. This is called metastasis.

Breast cancer can start in both women and men. Both women and men have breast tissue, and those cells can turn into cancer. Still, breast cancer is very rare in men.

The most common type of breast cancer in men is called infiltrating (or invasive) ductal cancer. This is cancer that starts in cells lining the milk ducts and spreads to nearby tissues.

Other less common types of breast cancer in men include ductal carcinoma in situ (DCIS), invasive lobular carcinoma, inflammatory breast cancer, and Paget disease of the nipple. A type of breast cancer called lobular carcinoma in situ is very rare in men. This is because men don't have much lobular tissue and it is not normally functional. (Lobular tissue is where breastmilk is made.)

Experts think that genes may play a role in breast cancer development in men. These include a family history of breast cancer in a first-degree relative and inherited changes (mutations) of the BRCA genes. Genes other than BRCA may also play a role. But each cancer case is different. Talk with your doctor about your own case.

A risk factor is anything that may increase your chance of having a disease. Risk factors for a certain type of cancer might include smoking, diet, family history, or many other things. The exact cause of someone's cancer may not be known. But risk factors can make it more likely for a person to have cancer.

Things you should know about risk factors for cancer:

• Risk factors can increase a person's risk, but they don't always cause the disease.
• Some people with one or more risk factors never develop cancer. Other people with cancer have no risk factors.
• Some risk factors are very well known. But there's ongoing research about risk factors for many types of cancer.

Some risk factors, such as family history, may not be in your control. But others may be things you can change. Knowing the risk factors can help you make choices that might help lower your risk. For instance, if an unhealthy diet is a risk factor, you may choose to eat healthy foods. If extra weight is a risk factor, your doctor may help you lose weight.

Risk factors for breast cancer in men include:

• Being age 60 or older
• Radiation exposure, such as from radiation used to treat another cancer in the chest
• Estrogen treatment (which might be used for prostate cancer)
• Diseases linked to high estrogen levels and low levels of male hormones (hyperestrogenism), such as severe liver disease or Klinefelter syndrome
• Heavy use of alcohol
• Being overweight or obese
• One or more female or male relatives have breast cancer
• A breast cancer 2 (BRCA2) gene mutation in the family

The most common symptoms of breast cancer in men include:

• Lump, thickening, or swelling in the breast or armpit that is often painless (but not always)
• Nipple that turns inward (inversion)
• Fluid leaking from the nipple (discharge) that may be bloody
• Skin or nipple changes, such as dimpling, puckering, redness, or scaling
• Changes in the size or shape of the breast

These symptoms might be caused by other health problems. But it's important to see a doctor right away if you have these symptoms. Only a doctor can tell if you have cancer.

Your doctor will ask about your health history and do a physical exam. A breast exam will be done. This means carefully feeling the breasts and under the arms for lumps or anything else that seems abnormal. Tests will also be needed. These may include:

• Ultrasound. This test uses sound waves to make pictures of internal organs or tissues.
• Mammogram. This is a low dose X-ray of the breast. A diagnostic mammogram is done when breast problems are present.
• MRI. This test takes detailed pictures of the inside of the body.
• Blood chemistry studies. Blood tests are done to measure the amounts of certain substances in the blood. Abnormal levels of certain substances can be a sign of disease.
• Biopsy. The doctor removes a tiny piece (sample) of cells or tissue so they can be tested for cancer. These are the types of biopsies:
  • Fine needle aspiration. A very thin hollow needle is put through the skin and into the lump to remove tissue or fluid.
  • Core needle biopsy. A wider hollow needle is used to take out larger cores of tissue. A vacuum suction may be used to assist removing tissue. The skin is numbed. Then a tiny cut is made in the skin to put the needle into the lump.
  • Excisional biopsy. This is done during surgery, and the doctor removes part or all of the lump.

If breast cancer is diagnosed, you'll need to have other tests done. These help your doctors learn more about your overall health and the cancer. They can help show if it has grown into nearby areas or spread to other parts of your body. The test results help your doctors decide the best ways to treat the cancer.

The stage of a cancer tells your doctor if and how far it has spread (metastasized) in your body. It's one of the most important things to know when deciding how to treat the cancer.

The staging system for male breast cancer is the same as the staging system for female breast cancer. It includes the size of the cancer and whether lymph nodes have cancer cells in them. It includes if the cancer has spread to distant sites. It also includes details about whether the cancer cells have certain proteins and how much they look like normal cells (called grade).

The stage is based on a 0 to 4 scale. It uses Roman numerals I (1), II (2), III (3), and IV (4). Stage 0 is also called carcinoma in situ. The cancer is small and only in the place where it first started. Stage IV means the cancer has spread to other parts of the body.

Your doctor will talk with you about what your cancer stage means and how it affects your treatment choices. Ask any questions or talk about your concerns.

The main treatment for male breast cancer is surgery. The most common surgery is a mastectomy. This means removing the breast tissue and the nipple. Sometimes lymph nodes under the arm, the lining over the chest muscles, and even part of the chest wall muscles under the breast are also removed.

Other treatments that may be used include:

Radiation therapy sends high-energy X-rays or beams of other particles right to the cancer cells. Radiation after surgery can kill cancer cells that may not be seen during surgery. Radiation may also be done before surgery to help shrink the tumor and make it easier to remove. It may be given along with chemotherapy. Or it may be used as a palliative treatment. This is a therapy that relieves symptoms, such as pain, but doesn't treat the disease.

Radiation therapy is usually given as external beam radiation. A large machine focuses the beams on the tumor. The machine is controlled by a radiation therapist. Special shields may be used to protect the tissue around the treatment area. Treatments are painless and often last a few minutes. Treatments are often given 5 days a week (Monday-Friday) for several weeks.

Chemotherapy (chemo) is the use of strong medicines to kill cancer cells. In most cases, chemo works by making the cancer cells unable to grow or divide. Different groups of medicines work in different ways to fight cancer cells. A doctor called a medical oncologist will work with you to make a treatment plan. Chemotherapy may be given before or after surgery.

In some cases, hormones can kill cancer cells, slow their growth, or stop them from growing. Hormone therapy as a cancer treatment uses medicines that affect the way certain hormones work or keep your body from making certain hormones. Before hormone therapy, your doctor will do a hormone receptor test. This lab test is done on a small piece of the cancer tissue to see if there are estrogen or progesterone receptors on the cells. A hormone receptor test can help to predict whether cancer cells are sensitive to hormones. If so, hormone therapy may be a treatment choice.

These medicines target certain proteins found on cancer cells. This limits the damage to healthy cells and can cause fewer and different side effects than chemo. Breast cancer cells are tested to see if they have a protein called HER2 on their surface. HER2 promotes cell growth, and these cancer cells tend to grow and spread quickly. There are targeted therapy medicines that attach to this protein to help stop cancer cell growth. Other targeted therapy drugs work on targets for BRCA mutations and hormone receptor positive cells.

Certain types of breast cancer can be treated with immunotherapy. This helps the body's immune system recognize and kill cancer cells. Immunotherapy may be used with chemotherapy.

• Though it's rare, men can get breast cancer.
• The most common type of breast cancer in men is infiltrating ductal cancer. This is cancer that starts in milk ducts and spreads to nearby tissues.
• Common symptoms of breast cancer in men are a breast lump or swelling, changes in the skin over the breast, or a nipple that turns inward (inversion).
• The main treatment for male breast cancer is surgery. The most common surgery is a mastectomy, which removes the breast tissue.

Tips to help you get the most from a visit to your doctor:

• Know the reason for your visit and what you want to happen.
• Before your visit, write down questions you want answered.
• Bring someone with you to help you ask questions and remember what your doctor tells you.
• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your doctor gives you.
• Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are.
• Ask if your condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if you do not take the medicine or have the test or procedure.
• If you have a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your doctor if you have questions, especially after office hours and on weekends and holidays.