Men may not realize that, for them too, any changes in their breasts, including lumps in the chest or underarm area—or changes to the nipple—could be a sign of breast cancer and should be checked out by a doctor.

Although breast cancer is far more prevalent in women, it can occur in men as well. Breast cancer in men, however, is less frequent, making up around 1% of all breast cancer diagnoses. In the U.S., there are around 2,650 cases each year and approximately 1 in 830 men will get breast cancer in their lifetime.

Since men are usually less familiar with its signs and symptoms—and because many are unaware that they can be affected by it—their breast cancer is often not diagnosed until it’s in a later, more advanced stage.

“Greater awareness of male breast cancer is needed and we believe in an all-inclusive care model for all individuals diagnosed with breast cancer,” says Maryam Lustberg, MD, MPH, director of The Breast Center at Smilow Cancer Hospital and chief of Breast Medical Oncology at Yale Cancer Center.

Like women, men have breast tissue (though they have less of it). Breast cancer occurs when cells in the breast tissue begin to grow and divide in an abnormal and uncontrolled manner. Over time, these cells can form tumors. Often, the tumors are benign, but sometimes, they are malignant, or cancerous. The cells that make up cancerous tumor can invade nearby tissues and may even migrate to—and form new tumors in—other parts of the body. The breast is made up of glandular, connective, and fatty tissues. The glandular tissues contain milk-producing glands called lobules and tube-like ducts that transport milk to the nipple. Cancer can develop in any of these tissues.

Several types of breast cancer can affect men, including:

• Ductal carcinoma. The most common type of breast cancer in men, ductal carcinoma develops in the breast ducts.
• Lobular carcinoma. This type of cancer develops in the lobules. Because men typically have few, if any, lobules, this type of breast cancer is rare, making up only around 1% of male breast cancers.

Other uncommon types of breast cancer that can occur in men include inflammatory, papillary, mucinous, medullary, and tubular breast cancers.

Ductal and lobular carcinomas can be invasive or non-invasive.

• Invasive breast cancers. These are cancers that originate in breast tissue such as the ducts or lobules and then spread to other tissues. Invasive ductal carcinomas (IDC) make up 80–90% of all male breast cancers. Invasive lobular carcinoma (ILC) is rare.
• Non-invasive breast cancers(“carcinoma in situ”). Cancer that develops in breast tissue but has not yet spread to other tissues in the body is called non-invasive. Ductal carcinoma in situ (DCIS) makes up around 7–11% of breast cancers in men. Lobular carcinoma in situ (LCIS) is rare.

As with female breast cancers, male breast cancers are also categorized based on their hormone receptor and HER2 status:

• Hormone receptor status. Hormones are chemicals that circulate in the body. Sometimes cancer cells contain receptors for certain hormones, in particular estrogen or progesterone, though some cancer cells have receptors for both hormones. These cancer cells are considered hormone receptor-positive, or HR-positive. The receptors allow the cells to bind to estrogen and/or progesterone, depending on the type of receptors present. These hormones promote the growth of HR-positive cancer cells.

• HER2 receptor status. HER2, or human epidermal growth factor receptor 2, is a protein found on the surface of cells in the breast. It helps regulate the growth of cells. Breast cancer cells that contain high levels of HER2 receptors, known as HER2-positive, tend to grow rapidly.

Breast cancer cells can be both HR-positive and HER2-positive. But they can also be “triple negative,” meaning they do not contain estrogen, progesterone, or HER2 receptors.

Non-modifiable risk factors—those that a person cannot change—for breast cancer include:

• Age. As men get older, their risk for breast cancer increases. The average age at diagnosis is 67.
• Family history of breast or ovarian cancer
• Cryptorchidism (being born with one or both testicles undescended)
• Genetics (mutations in certain genes including BRCA1 and BRCA2)
• Having diseases such as liver disease or Klinefelter syndrome that cause estrogen levels to rise in the body

Other risk factors that a man may be able to control or change include:

• Previous radiation therapy in the chest area
• Lack of exercise
• Obesity
• Alcohol consumption
• Estrogen treatment (used to treat prostate cancer)
• Gynecomastia (enlarged breasts)
  

Symptoms for breast cancer in men may include:

• Lump in the breast, often beneath the areola (usually painless)
• Lump(s) in the lymph nodes under the armpit nearest the affected breast
• Nipple changes (inverted nipple, rash or scales around nipple, nipple discharge)
• Reddening of breast skin
• Pitted or dimpled breast skin

Your doctor will begin to make a diagnosis by asking about your symptoms, whether you have taken or are currently taking certain medications associated with breast cancer, and whether you have any other known risk factors. A breast exam is also an important part of diagnosis. Your doctor will visually examine and feel your chest/breasts for signs of breast cancer.

Additional tests are required for diagnosis. Your doctor may order imaging tests such as a mammogram, ultrasound, or a magnetic resonance imaging (MRI) study of the affected breast. But to make a definitive diagnosis, a biopsy of the breast tissue is necessary. In this procedure, a small piece of breast tissue is removed, usually with a needle (though sometimes a surgical biopsy is required). A pathologist will analyze the tissue sample to check for the presence of cancer cells, and, if they are present, their hormone receptor and HER2 status.

If the biopsy confirms a diagnosis of breast cancer, your doctor will order more tests to see whether the cancer has spread beyond the breast. This is known as staging. It may involve additional imaging tests such as a chest X-ray, positron emission tomography (PET), or a bone scan. In some cases, a sentinel lymph node biopsy is necessary.

Once your doctor has determined the size and type of tumor and whether the cancer has spread to other parts of the body, he or she will assign the cancer to a stage. Staging helps doctors make a prognosis and design a patient-specific treatment plan.

Breast cancer is rare in men and according to the National Cancer Institute, “screening is unlikely to be beneficial.” Men who are higher risk for breast cancer, such as those who have BRCA mutations or a family history of breast and/or ovarian cancer should talk to their doctor about screening mammograms.

As with female breast cancer, standard treatments for male breast cancer include surgery, chemotherapy, radiation therapy, hormone therapy, and targeted therapy. The choice of treatment varies based on the stage of cancer, the tumor’s hormone receptor and HER2 status, and other factors.

• Surgery. The majority of men who have breast cancer undergo surgery to remove the tumor. Usually, this involves a mastectomy, which is the surgical removal of the entire breast, including the nipple and sometimes some of the underlying chest muscle and the lymph nodes under the neighboring armpit. In some cases, breast-conserving surgery may be an option. In this procedure, the surgeon takes out the tumor without removing the entire breast. 
• Chemotherapy. This treatment uses drugs to destroy cancer cells. It may be used after surgery, to ensure that any remaining cells are killed or before surgery, to reduce the size of the tumor. Chemotherapy is also used to treat cancers that have spread beyond the breast to other parts of the body.
• Radiation therapy. This treatment involves directing radiation, such as X-rays, at the tumor. The radiation kills the cancer cells, which stops them from growing and spreading. Radiation therapy is often used after surgery to ensure that any cancer cells that remain are destroyed. 
• Hormone therapy. Hormone receptor-positive breast cancers can be treated with hormone therapy. These mediations aim to deprive hormone receptor-positive cancer cells of the hormones that help them grow. Some of these drugs work by blocking the hormone receptors on cancer cells, which prevents hormones from binding to them. Other hormone therapy drugs work by reducing the production of estrogen and/or progesterone in the body. 
• Targeted therapy. Targeted therapies are designed to target specific proteins found in cancer cells. For instance, certain drugs specifically target the HER2 protein (in HER2-positive cancers) with the aim of slowing or stopping cancer cell growth. Other drugs are available target other proteins in breast cancer.

The outlook for men diagnosed with breast cancer depends on several factors including the stage at which the cancer is caught, the extent of spread, and type of tumor, among others. In general, the prognosis is best when the cancer is detected at an early stage. That’s why it is important for men who notice symptoms of breast cancer to see a doctor for evaluation.

After treatment, men should continue to follow up regularly with a doctor to monitor recovery and possible recurrence of breast cancer or the emergence of cancer elsewhere in the body.

“As with all types of breast cancer, we believe in a personalized, multidisciplinary approach to breast cancer in men,” says Dr. Lustberg. “The latest advances in breast cancer will be applied to ensure most optimal outcomes for each patient.”