What is Cancer?

Cancer is a group of many related diseases that begin in cells, the body’s basic building blocks. To understand cancer, it is helpful to know what happens when normal cells become cancerous.

The body is made up of many types of cells. Normally, cells grow and divide to produce more cells as they are needed to keep the body healthy. Sometimes, this orderly process goes wrong. New cells form when the body does not need them, and old cells do not die when they should. The extra cells form a mass of tissue called a growth or tumor. Not all tumors are cancerous; tumors can be benign or malignant.

Benign tumors are not cancer. They can often be removed and, in most cases, they do not come back. Cells in benign tumors do not spread to other parts of the body. Most important, benign tumors are rarely a threat to life.

Malignant tumors are cancer. Cells in malignant tumors are abnormal and divide without control or order. Cancer cells invade and destroy the tissue around them. Cancer cells can also break away from a malignant tumor and enter the bloodstream or lymphatic system.

Blood vessels include a network of arteries, capillaries, and veins through which the blood circulates in the body. The lymphatic system carries lymph and white blood cells to all the tissues of the body. By moving through the bloodstream or lymphatic system, cancer can spread from the original (primary) cancer site to form new tumors in other organs. The spread of cancer is called metastasis.

Symptoms & Risk Factors

Cancer is the second leading cause of death in this country. However, improvements in cancer detection, diagnosis, and treatment have increased the survival rate for many types of cancer. Get the facts and remain informed.

  • The most common sign of breast cancer is a new lump or mass. A mass that is painless, hard, and has irregular edges is more likely to be cancerous but some rare cancers are tender, soft, and rounded.
  • A generalized swelling of part of a breast (even if no distinct lump is felt).
  • Breast skin irritation or dimpling.
  • Nipple pain or retraction (turning inward), redness or scaliness of the nipple or breast skin.
  • Discharge other than breast milk.
  • Having early onset of menstrual periods or late menopause.
  • Never having children or having first child after age 30.
  • Obesity, especially after menopause.

Male Breast Cancer

How common is breast cancer in men? The American Cancer Society estimates for breast cancer in men in the United States for 2023 are:

  • About 2,790 new cases of invasive breast cancer will be diagnosed
  • About 530 men will die from breast cancer Breast cancer is about 100 times less common among White men than among White women. It is about 70 times less common among Black men than Black women. As in Black women, Black men with breast cancer tend to have a worse prognosis (outlook). For men, the average lifetime risk of getting breast cancer is about 1 in 726. The greatest risk factors for breast cancer in men include:
  • Aging: the average age of men with breast cancer is about 72.
  • Family history: about 1 out of 5 men with breast cancer have a close blood relative, male or female, with the disease.
  • Radiation exposure: A man whose chest area has been treated with radiation (such as for the treatment of a cancer in the chest, like lymphoma) has an increased risk of developing breast cancer.
  • Alcohol: heavy drinking increases the risk of breast cancer in men.
  • Obesity: fat cells in the body convert male hormones (androgens) into female hormones (estrogens). This means that obese men have higher levels of estrogens in their body.
  • Testicular conditions: certain conditions, such as having an undescended testicle, having mumps as an adult, or having one or both testicles surgically removed (orchiectomy) may increase male breast cancer risk.