Breast Cancer in Men

What Is Breast Cancer in Men?

Breast cancer is a malignant tumor that starts from cells of the breast. A malignant tumor is a group of cancer cells that may invade surrounding tissues or spread (metastasize) to distant areas of the body. Breast cancer occurs mainly in women, but men can get it, too. Many people do not realize that men have breast tissue and that they can develop breast cancer.

Normal breast structure

To understand breast cancer, it helps to have some basic knowledge about the normal structure of the breasts.

The breast is made up mainly of lobules (milk-producing glands in women), ducts (tiny tubes that carry the milk from the lobules to the nipple), and stroma (fatty tissue and connective tissue surrounding the ducts and lobules, blood vessels, and lymphatic vessels).

Until puberty (usually around age 13 to 14), young boys and girls have a small amount of breast tissue consisting of a few ducts located under the nipple and areola (area around the nipple). At puberty, a girl's ovaries make female hormones, causing breast ducts to grow, lobules to form at the ends of ducts, and the amount of stroma to increase. In males, hormones made by the testicles restrict further growth of breast tissue. Men's breast tissue contains ducts, but only a few if any lobules.

Like all cells of the body, a man's breast duct cells can undergo cancerous changes. But breast cancer is less common in men because their breast duct cells are less developed than those of women and because their breast cells are not constantly exposed to the growth-promoting effects of female hormones.

The lymph (lymphatic) system

The lymph system is important to understand because it is one of the ways that breast cancers can spread. This system has several parts.

Lymph nodes are small, bean-shaped collections of immune system cells (cells that are important in fighting infections) that are connected by lymphatic vessels. Lymphatic vessels are like small veins, except that they carry a clear fluid called lymph (instead of blood) away from the breast. Lymph contains tissue fluid and waste products, as well as immune system cells. Breast cancer cells can enter lymphatic vessels and begin to grow in lymph nodes.

Most lymphatic vessels in the breast connect to lymph nodes under the arm (axillary nodes). Some lymphatic vessels connect to lymph nodes near the breast bone (internal mammary nodes) and either above or below the collarbone (supraclavicular or infraclavicular nodes).

It's important to know if the cancer cells have spread to lymph nodes. If they have, there is a higher chance that the cells could have gotten into the bloodstream and spread (metastasized) to other sites in the body. This is important to know when you are choosing a treatment. The more lymph nodes that contain breast cancer, the more likely it is that the cancer may be found in other organs as well. Still, not all men with lymph nodes that contain cancer develop metastases, and in some cases a man can have negative lymph nodes and later develop metastases.

Benign breast conditions

Some breast disorders that can affect men are benign (not cancerous).

Benign breast tumors: There are many types of breast tumors (abnormal lumps or masses of tissue) that are benign, such as papillomas and fibroadenomas. Benign breast tumors do not spread outside of the breast and are not life threatening. Benign tumors are common in women but are very rare in men.

Gynecomastia: Gynecomastia is the most common male breast disorder. It is not a tumor but rather an increase in the amount of a man's breast tissue. Usually, men have too little breast tissue to be felt or noticed. A man with gynecomastia has a button-like or disk-like growth under his nipple and areola, which can be felt and sometimes seen. While gynecomastia is much more common than breast cancer in men, both can be felt as a growth under the nipple, which is why it's important to have any such lumps checked by your doctor.

Gynecomastia is common among teenage boys due to changes in the balance of hormones in the body during adolescence. It is also common in older men due to changes in their hormone balance.

In rare cases, gynecomastia occurs because tumors or diseases of certain endocrine (hormone-producing) glands cause a man's body to make more estrogen (the main female hormone). Men's glands normally make some estrogen, but it is not enough to cause breast growth. Diseases of the liver, which is an important organ in male and female hormone metabolism, can change a man's hormone balance and lead to gynecomastia. Obesity (being extremely overweight) can also cause higher levels of estrogens in men.

Some medicines can cause gynecomastia. These include some drugs used to treat ulcers and heartburn, high blood pressure, and heart failure. Men with gynecomastia should ask their doctors about whether any medicines they are taking might be causing this condition.

Klinefelter syndrome, a rare genetic condition, can lead to gynecomastia as well as increase a man's risk of developing breast cancer. This condition is discussed further in the section, "What are the risk factors for breast cancer in men?"

Breast cancer general terms

It may help to understand some of the key words used to describe breast cancer.

Carcinoma: This is a term used to describe a cancer that begins in the lining layer (epithelial cells) of organs such as the breast. Nearly all breast cancers are carcinomas (either ductal carcinomas or lobular carcinomas).

Adenocarcinoma: An adenocarcinoma is a type of carcinoma that starts in glandular tissue (tissue that makes and secretes a substance). The ducts and lobules of the breast are glandular tissue (they make breast milk in women), so cancers starting in these areas are sometimes called adenocarcinomas.

Carcinoma in situ: This term is used for the early stage of cancer, when it is confined to the layer of cells where it began. In breast cancer, in situ means that the abnormal cells remain confined to ducts (ductal carcinoma in situ, or DCIS) or lobules (lobular carcinoma in situ, or LCIS). They have not invaded into deeper tissues in the breast or spread to other organs in the body, and are sometimes referred to as non-invasive breast cancers.

Invasive (infiltrating) carcinoma: An invasive cancer is one that has already invaded beyond the layer of cells where it started (as opposed to carcinoma in situ). Most breast cancers are invasive carcinomas -- either invasive ductal carcinoma or invasive lobular carcinoma.

Types of breast cancer in men

Ductal carcinoma in situ (DCIS)

In DCIS (also known as intraductal carcinoma), cancer cells form in the breast ducts but do not invade through the walls of the ducts into the fatty tissue of the breast or spread outside the breast. DCIS accounts for about 1 in 10 cases of breast cancer in men. It is almost always curable with surgery.

Infiltrating (or invasive) ductal carcinoma (IDC)

This type of breast cancer breaks through the wall of the duct and invades the fatty tissue of the breast. At this point, it can spread (metastasize) to other parts of the body. IDC (alone or mixed with other types of invasive or in situ breast cancer) accounts for at least 8 out of 10 male breast cancers. Because the male breast is much smaller than the female breast, all male breast cancers start relatively close to the nipple, so spread to the nipple is more likely. This is different from Paget disease as described below.

Infiltrating (or invasive) lobular carcinoma (ILC)

This type of breast cancer starts in the breast lobules (collections of cells that, in women, produce breast milk) and invades the fatty tissue of the breast. ILC is very rare in men, accounting for only about 2% of breast cancers. This is because men do not usually have much lobular tissue.

Lobular carcinoma in situ (LCIS)

In LCIS, abnormal cells form in the lobules, but they do not invade into the fatty tissue of the breast or spread outside the breast. Although LCIS is sometimes classified as a type of non-invasive breast cancer, most breast specialists think it is a pre-cancerous condition rather than a true non-invasive cancer. As with invasive lobular carcinoma, LCIS is very rare in men.

Paget disease of the nipple

This type of breast cancer starts in the breast ducts and spreads to the nipple. It may also spread to the areola (the dark circle around the nipple). The skin of the nipple usually appears crusted, scaly, and red, with areas of itching, oozing, burning, or bleeding. Using the fingertips, a lump may be detected within the breast.

Paget disease may be associated with DCIS or with infiltrating ductal carcinoma. It accounts for about 1% of female breast cancers and a higher percentage of male breast cancers.

Do We Know What Causes Breast Cancer in Men?

Although certain risk factors may increase a man's chances of developing breast cancer, the cause of most breast cancers in men is unknown.

Hormone levels

Breast cells normally grow and divide in response to female hormones such as estrogen. The more cells divide, the more chances there are for mistakes to be made when they are copying their DNA. These DNA changes can eventually lead to cancer (see below).

Factors that change the ratio of female and male hormones in the body can therefore have an effect on breast cancer risk. Many of these were described in the section, "What are the risk factors for breast cancer?"

Gene changes (mutations)

Researchers are making great progress in understanding how certain changes in DNA can cause normal cells to become cancerous. DNA is the chemical in each of our cells that makes up our genes -- the instructions for how our cells function. We usually resemble our parents because they are the source of our DNA. However, DNA affects more than how we look.

Some genes contain instructions for controlling when our cells grow, divide, and die. Certain genes that speed up cell division are called oncogenes. Others that slow down cell division or cause cells to die at the appropriate time are called tumor suppressor genes. Cancers can be caused by DNA mutations (defects) that turn on oncogenes or turn off tumor suppressor genes.

Acquired gene mutations

Most DNA mutations related to male breast cancer occur during life rather than having been inherited before birth. It's not clear what causes most of these mutations. Radiation to the breast area is a factor in a small number of cases. Some acquired mutations of oncogenes and/or tumor suppressor genes may result from cancer-causing chemicals in our environment or diet, but so far studies have not identified any chemicals that are responsible for these mutations in male breast cancers.

Inherited gene mutations

Certain inherited DNA changes can cause a high risk of developing certain cancers and are responsible for cancers that run in some families.

Some breast cancers are linked to inherited mutations of the BRCA1 or BRCA2 tumor suppressor genes. Normally, these genes make proteins that help cells recognize and/or repair DNA damage and prevent them from growing abnormally. But if a person has inherited a mutated gene from either parent, the chances of developing breast cancer are higher.

In women, mutations of BRCA1 and BRCA2 are responsible for about 5% to 10% of breast cancers. Women with either of these altered genes have a lifetime breast cancer risk of up to 80%.

In men, changes in the BRCA2 gene seem to be responsible for about 10% of breast cancer cases. The lifetime breast cancer risk for men with BRCA2 mutations is about 5% to 10%, which is much higher than for other men.

BRCA1 seems to play a role in only a small number of male breast cancers, but it may be more common in Jewish men. Recent studies suggest that BRCA1 mutations may increase the lifetime risk of breast cancer in men to about 1%.

Genetic testing

Genetic testing can be done to look for mutations in the BRCA1 and BRCA2 genes (or less commonly in other genes related to breast cancer). Testing may be helpful in some situations,but the pros and cons need to be considered carefully. For more information, see the section, "Can breast cancer in men be found early?"

Can Breast Cancer in Men Be Found Early?

Early detection improves the chances that male breast cancer can be treated successfully.

Differences between male and female breast cancers

There are many similarities between breast cancer in men and women, but some important differences affect early detection.

The most obvious difference between the male and female breast is size. Because men have very little breast tissue, it is easier for men and their health care professionals to feel small masses. On the other hand, because men have so little breast tissue, cancers do not need to grow very far to reach the nipple, the skin covering the breast or the muscles underneath the breast. So even though breast cancers in men tend to be slightly smaller than in women when they are first found, they have more often spread beyond the breast. The extent of spread beyond the breast is one of the most important factors in the prognosis (outlook) of a breast cancer.

Another difference is that breast cancer is common among women and rare among men. Women tend to be aware of this disease and its possible warning signs, while most men do not realize they have even a small risk of being affected. Some men ignore breast lumps or think they are caused by an infection or some other reason, and they do not get medical treatment until the mass has had a chance to grow. Some men are embarrassed about finding a breast lump and worry that someone might question their masculinity. This may also delay diagnosis and reduce a man's odds for successful treatment.

Because breast cancer is so uncommon in men, there is unlikely to be any benefit in screening men in the general population for breast cancer.

For men who are or may be at high risk

Mammography (x-rays of the breast) along with careful breast exams might be useful for screening men with a strong family history of breast cancer and/or with BRCA mutations found by genetic testing. Men with such a history should discuss this with their doctor.

Genetic testing

If you have a strong family history of breast cancer (in men or women) and/or ovarian cancer that might be caused by a BRCA mutation, you may want to consider genetic testing to determine if you have inherited a mutated BRCA gene. If the test detects a mutated BRCA gene, you and your health care team can watch carefully for early signs of cancer. Mammography can be effective in finding early breast cancer in men.

If you are thinking about genetic testing, it is strongly recommended that you talk first to a genetic counselor, nurse, or doctor qualified to explain and interpret these tests. It is very important to understand what genetic testing can and can't tell you, and to carefully weigh the benefits and risks of testing before these tests are done. Test results are not always clear cut, and even if they are, it's not always clear what should be done about them. There may be other concerns as well, such as what the results might mean for other family members. Testing is also expensive and may not be covered by some health insurance plans.

For more information, see our separate document, Genetic Testing: What You Need to Know. You may also want to visit the National Cancer Institute Web site (www.cancer.gov/cancertopics/Genetic-Testing-for-Breast-and-Ovarian-Cancer-Risk).

There have been concerns that people with abnormal genetic test results might not be able to get health or other insurance or that coverage may only be available at a much higher cost, but many states have passed laws that prevent insurers from denying insurance on the basis of genetic testing. The federal government has also passed a law (going into effect in May 2009) that bars discrimination by health insurers or employers based on genetic information, although it does not address life insurance or other areas. To learn about state laws against genetic testing discrimination, you may want to visit the Web site of the National Conference of State Legislatures (www.ncsl.org/programs/health/genetics/ndishlth.htm).

How Is Breast Cancer in Men Treated?

This information represents the views of the doctors and nurses serving on the American Cancer Society's Cancer Information Database Editorial Board. These views are based on their interpretation of studies published in medical journals, as well as their own professional experience.

The treatment information in this document is not official policy of the Society and is not intended as medical advice to replace the expertise and judgment of your cancer care team. It is intended to help you and your family make informed decisions, together with your doctor.

Your doctor may have reasons for suggesting a treatment plan different from these general treatment options. Don't hesitate to ask him or her questions about your treatment options.

Most of the information about treating male breast cancer comes from doctors' experience with treating female breast cancer. Because there are so few men with breast cancer, it is hard for doctors to study their treatment separately in clinical trials.

This section starts with general comments about the types of treatments used for breast cancer. This is followed by a discussion of the typical treatment options based on the stage of the cancer.