Cancers
Cancer results when body cells grow in an uncontrolled manner. Normal cells in the body follow an orderly path of growth, division, and death. Programmed cell death is called apoptosis, and when this process breaks down, cancer begins to form. Unlike regular cells, cancer cells do not experience programmatic death and instead continue to grow and divide. This leads to a mass of abnormal cells that grows out of control.
Cancer harms the body when damaged cells divide uncontrollably to form lumps or masses of tissue called tumours. Tumours can grow and interfere with the digestive, nervous, and circulatory systems, and they can release hormones that alter body function. Tumours that stay in one spot and demonstrate limited growth are generally considered to be benign. More dangerous, or malignant, tumours form when two things occur: a cancerous cell manages to move throughout the body using the blood or lymph systems, destroying healthy tissue in a process called invasion, and secondly that cell manages to divide and grow, making new blood vessels to feed itself in a process called angiogenesis.
Cancers can be caused by a variety of factors. Cancer can be the result of a genetic predisposition that is inherited from family members. It is possible to be born with certain genetic mutations or a fault in a gene that makes one statistically more likely to develop cancer later in life. Carcinogens are a class of substances that are directly responsible for damaging DNA, promoting or aiding cancer. Tobacco, asbestos, arsenic, radiation such as gamma and x-rays, the sun, and compounds in car exhaust fumes are all examples of carcinogens. When our bodies are exposed to carcinogens, free radicals are formed that try to steal electrons from other molecules in the body. Theses free radicals damage cells and affect their ability to function normally.
As we age, there is an increase in the number of possible cancer-causing mutations in our DNA. This makes age an important risk factor for cancer. Several viruses have also been linked to cancer such as: human papilloma virus (a cause of cervical cancer), hepatitis B and C (causes of liver cancer), and Epstein-Barr virus (a cause of some childhood cancers). Human immunodeficiency virus (HIV) - and anything else that suppresses or weakens the immune system - inhibits the body's ability to fight infections and increases the chance of developing cancer.
There are various types of cancer, and each is classified by the type of cell that is initially affected.
- Bladder cancer - occurs when abnormal cells multiply without control in the bladder, most commonly in the cells that make up the inner lining of the bladder.
- Breast cancer - occurs when some breast cells begin growing abnormally.
- Colorectal cancer - is an umbrella term which refers to both colon cancer, which is the cancer of the large intestine (colon), together with rectal cancer which is cancer of the last several inches of the colon.
- Gastric cancer – cancer that starts in the cells of the stomach.
- Lung cancer – occurs when there is abnormal cell division in the cells of the lungs.
- Prostate cancer - occurs when cells within the prostate, a gland in the male reproductive system, grow uncontrollably creating small tumours.
- Skin cancer - is a malignant growth on the skin which can have many causes. Skin cancer generally develops in the epidermis (the outermost layer of skin), so a tumour is usually clearly visible.