What Is Cancer And What Causes It

Cancer refers to any one of a large number of diseases characterized by the development of abnormal cells that divide uncontrollably and have the ability to infiltrate and destroy normal body tissue. Cancer often has the ability to spread throughout your body.

Cancer is the second-leading cause of death in the United States. But survival rates are improving for many types of cancer, thanks to improvements in cancer screening and cancer treatment.


Signs and symptoms caused by cancer will vary depending on what part of the body is affected.

Some general signs and symptoms associated with, but not specific to, cancer, include:

  • Fatigue.
  • Lump or area of thickening that can be felt under the skin.
  • Weight changes, including unintended loss or gain.
  • Skin changes, such as yellowing, darkening or redness of the skin, sores that won’t heal, or changes to existing moles.
  • Changes in bowel or bladder habits.
  • Persistent cough or trouble breathing.
  • Difficulty swallowing.
  • Hoarseness.
  • Persistent indigestion or discomfort after eating.
  • Persistent, unexplained muscle or joint pain.
  • Persistent, unexplained fevers or night sweats.
  • Unexplained bleeding or bruising.

For most cancers the causes are not fully understood. However, some factors that place individuals at a greater risk for cancer are well-recognized.

  • Tobacco smoking
  • Alcohol consumption
  • Diet – for example, high intake of particular foods (such as processed meat and foods that are high in fat) is associated with an increased risk for some types of cancer
  • Overweight and obesity
  • physical inactivity
  • UV radiation
  • Infections – for example, some types of human papillomavirus (HPV) infection can be associated with cervical and other cancers, and chronic hepatitis B or C
  • Infection can be associated with liver cancer
  • Occupational exposure to agents, including chemicals, dusts and industrial processes
  • Family history and genetic susceptibility – some genes that can predispose a person to cancer can be passed on from parent to child

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