Cancer is the word we use to describe a group of diseases that start in cells and then grow out of control. This growth can affect the whole body or a particular part of it. Some cancers are cured, but others return even after treatment. Most cancers are not hereditary and most of them start because of gene changes that happen slowly over a person’s lifetime.
Cells are the smallest units that make up the body’s tissues and organs. The genes in a cell decide whether the cell grows, divides (multiplies), becomes specialized to perform a certain task, or dies and is replaced by another healthy cell. Changes in genes are called mutations. Mutations can occur when normal cells divide or when damaged cells repair themselves. Cells that have genetic changes that give them a survival advantage over other cells will multiply and spread to other parts of the body, forming tumors.
Most of us know someone who has had cancer. But few of us understand how cancer develops and how it is categorized. Most general definitions of cancer are too broad and do not include important aspects of the disease. They often describe what a cancer “looks like” or “does,” but do not capture the way in which cancers develop, spread and resist treatment.
Normally, cells in the body divide to produce new cells as they need them. Old cells are then either recycled or die to be replaced by new cells. Cancers interrupt this orderly process by dividing without stopping, spreading into surrounding tissues and other parts of the body, and resisting treatment.
When cancers are detected, they may be described as a lump or mass that forms in the skin or other body tissue. The term “tumour” is also used to describe an abnormal area of the body that is not a cancer, but that can cause problems, such as when tumours press on or interfere with other organs. Cancers are also characterized by their grade and stage. Grading describes how fast the cancer is growing and how likely it is to spread to other parts of the body.
Signs and symptoms of cancer are many and varied. They can range from pain or a lump in the skin to unexplained weight loss, fatigue that does not improve with rest, a change in bowel habits (like diarrhea or constipation), a persistent fever, and yellowing of the eyes and skin (jaundice).
Scientists have found some things that reduce a person’s risk of developing cancer. These include eating a balanced diet that includes fruits and vegetables, whole grains, lean proteins, and healthy oils; avoiding high levels of sodium, sugar, and alcohol; and getting plenty of exercise. Currently, however, there is no single food, nutrient or vitamin that can prevent cancer.