More than 1.6 million new cancer diagnoses will occur this year in the United States; more than 500,000 Americans will likely die from cancer. Nearly everyone personally knows someone who has been directly affected by cancer. Beyond its toll on human lives, the financial cost of cancer care in America exceeded $216 billion in 2013, according to the National Institutes of Health.

Cancer is a familiar term, but exactly what is cancer?

The definition of cancer is a disease caused by the uncontrolled growth of abnormal cells within the body.

While you should not make health care decisions without consulting a qualified physician, this basic information can help you to improve your knowledge of cancer. In this section, you can learn about some of the more commonly diagnosed cancers. 

Breast Cancer

Breast Cancer

  • Leading cancer cause of death in women.
  • Average lifetime risk in women is around 1 in 8.

Prostate Cancer

Prostate Cancer

  • Average lifetime risk in men is around 1 in 7.
  • Leading cancer cause of death in men.

Lung Cancer

Lung Cancer

  • Second most common cancer in men and women.
  • Accounts for more than one-quarter of all cancer deaths.

Colorectal Cancer

Colorectal Cancer

  • Third most common non-skin cancer in men and women.
  • Third leading cancer cause of death in men and women.

Ovarian Cancer

Ovarian Cancer

  • Fifth leading cause of cancer death among women.
  • Five-year survival rate of 45 percent.

Pancreatic Cancer

Pancreatic Cancer

  • Accounts for 3 percent of all cancers and 7 percent of all cancer deaths.
  • Five-year survival rate of 7 percent.

Leukemia Cancer

Leukemia

  • Accounts for around 1 in 3 cancers diagnosed in children.
  • Five-year survival rate of 59 percent.

Lymphoma Cancer

Non-Hodgkin's Lymphoma

  • Average lifetime risk is around 1 in 50.
  • Five-year survival rate for non-Hodgkin's lymphoma is 71 percent.

Lymphoma Cancer

Hodgkin's Lymphoma

  • More than 1 in 10 cancer cases diagnosed in children and teens.
  • Five-year survival rate for Hodgkin's lymphoma is 85 percent.

How does cancer start?

Cancer Cells

The human body is made up of trillions of living cells. Genetic material, or DNA, contained within these cells provides instruction how they should behave. Healthy cells generally act in predictable ways.

How healthy cells behave

  • They replicate themselves and reproduce at specified times.
  • They cease the process of replication and reproduction at specified times.
  • They stay in appropriate parts of the body.
  • They die at an appropriate time when their function has been fulfilled.

Sometimes cells develop with errors to their DNA. Cells are often able to repair themselves or cease functioning when these errors occur. Cancer begins when cells with damaged DNA fail to self-repair and instead grow out of control.

How cancer cells behave

  • They reproduce and replicate uncontrollably.
  • They grow beyond the part of the body where they belong, invading other parts of the body.
  • They do not die or cease functioning when they are supposed to. 

Cancer Categories

Cancer Types

While individual cancers are usually named for the part of the body where they begin, these can be grouped into broader categories.

Carcinoma

Carcinomas are cancers that begin in the skin or in the layers of cells that line the surfaces of internal organs.

Sarcoma

Sarcomas are cancers that begin in the bones or soft connective tissue, such as cartilage, fat, muscle and blood vessels.

Leukemia

Leukemia refers to a group of cancers that usually begin in bone marrow, which produces blood cells, and results in abnormalities to a large number of blood cells.

Lymphoma/Myeloma

Lymphoma refers to cancers that develop within white blood cells. These cells are a central component to the immune system that helps to fight disease. While there are more than 80 forms of lymphomas, these cancers are sometimes separated into broad sub-groups. This includes Hodgkin’s lymphoma, non-Hodgkin’s lymphoma, myeloma and immunoproliferative disorders.

Central Nervous System Cancers

Central nervous system cancers are those that begin in brain tissue or the spinal cord.