What Is Breast Cancer in Men?
Breast cancer is a malignant tumor that has developed from cells of the breast. The disease occurs primarily in women but occasionally occurs in men. Many people do not realize that men have breast tissue and that they can develop breast cancer.
Normal Breast Structure
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 in women), and stroma (fatty tissue and connective tissue surrounding the ducts and lobules, blood vessels, and lymphatic vessels).
Until puberty, 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 produce female hormones, causing breast ducts to grow, lobules to form at the ends of ducts, and the amount of stroma to increase. On the other hand, male hormones produced by the testicles prevent 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. Because women have many more breast cells than men do and perhaps because their breast cells are constantly exposed to the growth-promoting effects of female hormones, breast cancer is much more common in women.
Many types of breast disorders can affect both men and women. Most breast disorders are benign (not cancerous). Benign breast tumors do not spread outside of the breast and are not life threatening. Other tumors are malignant (cancerous) and may become life threatening. Benign tumors, such as papillomas and fibroadenomas, are common in women but are extremely rare in men.
As in most tissues of the body, fluids are circulated to and from the breast by 2 main forms of channels. Blood vessels carry blood to and from the breast. Lymphatic vessels carry lymph instead of blood. Lymph is a clear fluid that contains tissue fluid and waste products and immune system cells (cells that are important in fighting infections). Lymph nodes are small, bean-shaped collections of immune system cells that are found along lymphatic vessels. This is important in cancer, because cancer cells can enter lymphatic vessels and spread to lymph nodes. This becomes important when we talk about staging (see ”Staging” section).
Most lymphatic vessels in the breast connect to lymph nodes under the arm (axillary lymph nodes). Some lymphatic vessels connect to lymph nodes inside the chest (internal mammary nodes) and either above or below the collarbone (supraclavicular or infraclavicular nodes).
Knowing if the cancer cells have spread to lymph nodes is important because that lets us know that there is a higher chance that the cells could have gotten into the bloodstream and spread to other sites in the body. This is why it is important to find out if breast cancer has spread to your axillary lymph nodes when you are choosing a treatment. The more lymph nodes that are involved with the breast cancer, the more likely it is that the cancer will eventually be found in other organs as well. However, not all men with lymph node involvement develop metastases, and it is not unusual for a man to have negative lymph nodes and later develop metastases.
Benign Breast Conditions
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. Gynecomastia, common among teenage boys, is due to changes in hormone balance during adolescence. The same condition is also common in older men and is also due to changes in their hormone balance.
Rarely, gynecomastia occurs because tumors or diseases of certain endocrine (hormone-producing) glands cause a man's body to produce more estrogen (the main female hormone). Although men's glands normally produce some estrogen, 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 may be another cause of elevated estrogens in men.
Many commonly prescribed medicines can sometimes cause gynecomastia, too. 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 and increase a man's risk of developing breast cancer. This condition is discussed further in the section on risk factors for male breast cancer.
Types of Breast Cancer
Adenocarcinoma: Nearly all breast cancers start in the ducts or lobules of the breast. Because this is glandular tissue, they are called adenocarcinomas, a term applied to cancers of glandular tissue anywhere in the body. The 2 main types of breast adenocarcinomas are ductal carcinomas and lobular carcinomas.
Ductal carcinoma in situ (DCIS): DCIS is an uncommon type of breast adenocarcinoma in men (about 10%). Cancer cells fill the ducts but do not invade through the walls of the ducts into the fatty tissue of the breast or spread outside the breast. It is almost always curable with surgery.
In situ is the term used for the early stage of cancer, when it is confined to the immediate area where it began. Specifically in breast cancer, in situ means that the cancer remains confined to ducts (ductal carcinoma in situ) or lobules (lobular carcinoma in situ). It has not invaded surrounding fatty tissues in the breast nor spread to other organs in the body.
Infiltrating (or invasive) ductal carcinoma (IDC): Starting in a duct of the breast, this type of adenocarcinoma breaks through the wall of the duct and invades the fatty tissue of the breast. At this point, it can metastasize (or spread) to other parts of the body. IDC (alone or mixed with other types of invasive or in situ breast cancer) accounts for 80% to 90% of male breast cancers.
Lobular breast cancers in men are very rare, accounting for only 2% of adenocarcinomas. This is because men do not usually have lobular tissue, the milk-producing glands.
Paget disease of the nipple: This type of breast cancer starts in the breast ducts and spreads to the skin of 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. If no lump can be felt, the prognosis (outlook for survival) is generally good. Paget disease may be associated with in situ carcinoma or with infiltrating breast carcinoma. It accounts for about 1% of female breast cancers and a higher percentage of 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.
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.
Researchers are making great progress in understanding how certain changes in DNA can cause normal cells to become cancerous. DNA is the chemical that carries the instructions for nearly everything our cells do. We usually resemble our parents because they are the source of our DNA. However, DNA affects more than our outward appearance.
Some genes (parts of our DNA) contain instructions for controlling when our cells grow, divide, and die. Certain genes that promote 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 activate oncogenes or inactivate tumor suppressor genes. Certain inherited DNA changes can cause a high risk of developing certain cancers and are responsible for cancers that run in some families.
Most DNA mutations related to male breast cancer occur during life rather than having been inherited before birth. 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 individual chemical in the environment or in our diet that appears responsible for these mutations or the subsequent male breast cancers.
Genetic risk factors: Some breast cancers are linked to inherited mutations of the BRCA tumor suppressor genes. Normally, these genes make a protein that helps cells recognize and/or repair DNA damage and prevents them from growing abnormally. However, if a person has inherited a mutated gene from either parent, the chances of developing breast cancer are higher. In women, mutations of 2 different BRCA genes (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 85%.
In men, the BRCA2 gene is responsible for about 5% to 10% of breast cancer cases. Some studies have found even higher rates. The lifetime breast cancer risk for men with BRCA2 mutations is about 7%, which is nearly 100 times greater than other men. In Jewish men, BRCA1 can play a role in a small number.
Testing of your DNA from blood samples can determine if you have inherited a mutated BRCA2 gene. This should only be done if you have a strong family history of breast cancer and/or ovarian cancer suspected to be caused by the BRCA2 mutation. If the test detects a mutated BRCA2 gene, you and your health care team can watch carefully for early signs of cancer. Mammography is very effective in finding early breast cancer in men. The health care team also can warn close male and female relatives that they also may be at risk.
The role of BRCA1 mutations in male breast cancer is less clear. Recent studies suggest that BRCA1 mutations may slightly increase the risk of breast cancer in men, although by a much smaller extent than BRCA2 mutations. A large study found about half as many BRCA1 mutations in men with breast cancer as BRCA2 mutations. Both BRCA genes can also increase a man’s risk for certain other cancers, such as prostate cancer.
If you are considering genetic testing, you should speak to a genetic counselor or a doctor specially qualified in interpreting and explaining these test results. For additional information, see our policy statement on genetic testing.Can Breast Cancer in Men Be Found Early?
Early detection improves the chances that male breast cancer can be treated successfully. Many men's breast cancers could have been found earlier by their health care professional with regular checkups.
Differences Between Male and Female Breast Cancers: Relevance to Early Detection
Although there are many similarities between breast cancer in men and women, several 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 skin covering the breast or the muscles underneath the breast. Therefore, although male breast cancers tend to be slightly smaller than female breast cancers when they are first found, they have more often spread beyond the breast. The extent of spread beyond the breast is the most important factor in the prognosis (outlook for chances of survival) of a breast cancer.
Another difference is that breast cancer is common among women and rare among men. So many women are aware of this disease, 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 grown significantly. Also, some men who think breast lumps occur only in women are embarrassed about finding one and worry that someone might question their masculinity. This attitude may also delay diagnosis and reduce a man's odds for successful treatment.
Because breast cancer is so uncommon, there is no value in screening mammography in most men. However, mammography along with careful examination might be useful as a screening examination for men with a strong family history and BRCA mutations found by genetic testing.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. There are too few men with breast cancer for doctors to study in clinical trials.