Topic Overview

What is male breast cancer?

Breast cancer in men is rare. Out of 100 cases of breast cancer, one case occurs in an adult male.¹ It develops in the small amount of breast tissue found behind a man's nipple.

What causes male breast cancer?

Although the exact cause of breast cancer is not known, most experts agree that some men have a greater risk for breast cancer than others. In the United States, male breast cancer mostly affects men age 65 and older.¹

The things that most increase a man's risk of breast cancer include:¹

• Inheriting mutations in the BRCA1 and BRCA2 genes.
• Having Klinefelter syndrome, a genetic disorder in which an extra chromosome is present.

Other things that increase a man's risk include:

• Having a history of breast disease that was not cancer.
• Having enlarged breasts (gynecomastia).

What are the symptoms?

The most common symptom of male breast cancer is a painless lump or swelling behind the nipple. Other symptoms can include a discharge from the nipple or a lump or thickening in the armpit. Although most men diagnosed with breast cancer are older than 65, breast cancer can appear in younger men. For this reason, any breast lump in an adult male is considered abnormal and should be checked out by a doctor.

How is male breast cancer diagnosed?

Most male breast cancer is diagnosed with a biopsy to investigate a lump or thickening in the breast or armpit. Because there is no routine screening for breast cancer and a breast lump does not usually cause pain, sometimes breast cancer isn't discovered until it has spread to another area of the body and is causing other symptoms.

How is it treated?

The main treatment for male breast cancer is surgery (total mastectomy) to remove the breast and sentinel lymph node biopsy. Because most men do not have very much breast tissue, breast-conserving surgery (lumpectomy) is not used.

There hasn't been much research on breast cancer treatments in men, because male breast cancer is so uncommon. But breast cancer in men is similar to breast cancer in women, and some of the same treatments may be used. These include radiation therapy, chemotherapy, hormone therapy, and targeted therapy.

Chemotherapy may be used after surgery to reduce the chance that breast cancer will come back somewhere else in the body. If the breast cancer is sensitive to certain hormones (meaning that the cells have estrogen/progesterone receptors), male breast cancer may be treated with a hormone-blocking agent called tamoxifen. Male breast cancer usually responds very well to chemotherapy or hormone therapy.

For more information about specific breast cancer treatments, see the topics:

• Male Breast Cancer Treatment—Health Professional Information [NCI PDQ].
• Male Breast Cancer Treatment—Patient Information [NCI PDQ].

What to think about

Male breast cancer is rare and makes up only about 1% of all breast cancers discovered each year. For this reason, many experts encourage men with breast cancer to talk to their doctors about clinical trials. These trials continue to look for better ways to treat male breast cancer.