Cancer

• Cancer

  Cells grow then divide by mitosis only when we need new ones – when we’re growing or need to replace old or damaged cells.
• When a cell becomes cancerous, it begins to grow and divide uncontrollably. New cells are produced – even if the body does not need them.
• Types of Tumor: Benign Characteristics: Grows slowly; usually grows within a membrane, so can easily be removed; does not invade other parts of the body
• Malignant Characteristics: Grows quickly; spreads through blood vessels and lymphatic system; may form secondary tumors (metastases) elsewhere in the body
• Benign tumours do not spread to other parts of the body but malignant tumours do
• What causes cancer?

  There are genetic factors that increase the likelihood of developing some cancers.

  Chemicals and other agents that can cause cancer are called carcinogens.
• Carcinogens cause cancer by damaging DNA. Carcinogens cause mutations to occur. A single mutation will not cause cancer – several are required. For this reason, we are more likely to develop cancer as we get older.
• Something that increases the likelihood of developing a disease is called a risk factor. There are several risk factors for various types of cancers including: Lifestyle factors
• Lifestyle factors:

  • viruses linked with cancer, such as the human papilloma virus (HPV), being spread from person to person through sexual intercourse
  • the chemical carcinogens in cigarette smoke increase the risk of lung cancer
  • alcohol intake is linked with certain cancers
  • exposure to ultraviolet radiation, part of which is ionising, during sunbathing or outdoor activities, leading to the development of skin cancers
  • diet, including fat and salt intake, increases the risk of cancer
• Industrial and environmental factors at work:

  • exposure to ionising radiation increases the risk factor
  • exposure to chemical carcinogens

  There are also genetic risk factors for some cancers.

  Next pageRisk factors and causal mechanismsPrevious page