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CancerCancer is the new growth of tissue resulting from a continuous proliferation of abnormal cells that have the ability to invade and destroy other tissues. Cancer which may arise from any type of cell and in any body tissue is not a single disease but a large number of diseases classified according to the tissue and type of cell of origin. Several hundred such classes exists constituting three major subtypes. The first sarcomas arise from connective and supportive tissue such as bone cartilage, nerve, blood vessels, muscle, and fat. The second carcinomas which include the most frequently occurring forms of human cancer arise from epithelial tissue such as the skin and the lining of the body cavities, organs and glandular tissue such as that of the breast and prostate.
Carcinomas with a flaky structure resembling skin are termed squamous-cell carcinomas. Those that resemble glandular tissue are called adenocarcinomas. The third subtype, leukemias and lymphomas, include the cancers that involve blood-forming tissue and are typified by the enlargement of the lymph nodes the invasion of the spleen and bone marrow and the overproduction of immature white blood cells.
PROGNOSIS AND THE LONG-TERM PICTURE
Many people are now successfully treated for cancer. The modern approach to cancer treatment also includes an emphasis on the patient 's quality of life both physical and mental.
There are many forms of cancer where the chances of survival are many times better than they were just a few years ago. Developments in the field of children?s cancers are perhaps the most encouraging.
The death rate from cancer has fallen progressively in people under 50 probably because healthier habits and environment have reduced prolonged exposure to carcinogens. Earlier diagnosis which is absolutely vital in all cases and improved treatments are also involved. This drop is expected to extend to older age groups as these younger people age.
Decreases in the number of smokers in some countries are starting to have an impact on the cancer figures. For instance, in the United Kingdom the number of deaths from lung cancer in men has finally started to decline. Unfortunately, the number of women dying from it is still going up ; Scottish women have the highest rate of death from lung cancer in the world.
The overall risk of death from cancer has increased over the past 30 years. This is because cancer is mainly a disease of older age and, as greater success is achieved at preventing early deaths from other illnesses such as heart disease; more people are living long enough to reach an age where their cancer risk increases.
HOW CANCER ARISES
Our bodies are made up of cells. Throughout our lives most of these cells are being continually replaced by a process of cellular division in which each cell divides itself into two similar, daughter cells. Each of these daughter cells which have the same characteristics as the original cells will in turn divide. This process of reduplication is called mitosis and is taking place within our bodies all the time. Approximately every four months for example all our red blood cells are completely replaced by a new generation of red blood cells. Similarly over a period of about eight months, all our old skin is shed and replaced by a completely new layer.
We are unaware of this continual process of reduplication but it nevertheless occurs and does so for good reason. For tissues to remain functional, they must be composed of cells that are operating to their full potential. To take an example red blood cells have a very important role in that they carry oxygen to the various tissues in the body. As these cells age however their efficiency is impaired and they become less able to perform this function adequately. Now if there were no mechanism to replace these ageing red blood cells, all our tissues would soon become starved of oxygen. So the process of cellular renewal revitalization and reduplication is the very foundation upon which our bodies remain in a healthy state.
In normal conditions our bodies have evolved a delicate mechanism for controlling the rate at which new cells form and reduplicate. When this control mechanism breaks down certain cells in the body begin in reduplicate in an uncontrolled way. It is when this happens that the problem is said to be cancerous.
To reiterate then cancer occurs when a small group of cells within normal tissue begins to reduplicate in an uncontrolled manner.
WHAT CAUSES CANCEROUS CELLS TO GROW AND DIVIDE UNCHECKED
A normal cell has a nucleus which in turn contains genes. Genes are made up of a chemical called deoxyribonucleic acid (DNA). When a cell divides, it does instructions from its genes. In order for this to occur the DNA receives chemical instructions to take up a particular configuration before initiating the process of division. It is probably in or around this chemical controlling mechanism upon which the action of he DNA is dependent that the basic cause of cancer is to be found. It is thought to be at this level of chemical involvement that the DNA may sometimes receive disorganized and incorrect instructions. In other words, instead of being instructed to initiate the process of cellular reduplication in an orderly and regular way, it receives a garbled or incomplete set of chemical instructions, which makes it initiate cellular reduplication, but in a haphazard and uncontrolled manner resulting in a mass of irregularity dividing cancerous cells.
WHAT CAUSES THE CELLULAR DUPliCATION TO MALFUNCTION:
There are two basic influences upon this DNA. One is the influence that the DNA has upon itself i.e. the genetic information that it contains. As a composite whole these are the gees our hereditary blueprints, passed from generation to generation. In certain individuals, families and racial groupings however this genetic information can cause the reduplicating mechanism of the cell to malfunction. We often refer to this type of situation as hereditary predisposition. So within an individual cell there may be a hereditary predisposition to cancer.
As well as this either in combination or independently the DNA can be influenced by external chemical stimuli which can lead to the haphazard and uncontrolled cellular division which is the characteristic hallmark of cancer. These external stimuli include among others viruses, hormones, harmful chemicals and ionizing radiation.
Virus - There has always been a school of scientific thought that has strongly believed that the basic cause of many cancers can be attributed to viral infection. But while there are well documented cases of viruses causing cancer in animals, there is on the whole little evidence for this in humans. However specifically there are three rate cancers which are almost certainly caused by viruses. These are human T-cell leukemia, Burkett?s leukemia and nasopharyngeal carcinoma. Similarly viral particles have been isolated in cancers of the breast and liver though the significance of such particles is still very much open to debate. One of the major problems when considering whether or not viruses are a cause of cancer is the fact that when they enter body tissues, viruses tend to set up an inflammatory reaction. This inflammatory reaction can then become chronic and it is possible that if the cells of the involved tissues become cancerous, the malignancy may be due to chronic inflammation, rather than from the viral particles themselves.
Smoking - Smoking is one of the biggest causes of premature death in the Western world. Not only does it cause over one third of cancers, but it also causes heart disease and major forms of lung disease, such as chronic bronchitis and emphysema. Smoking has already killed 60 million people worldwide since 1950 and is likely to kill half a billion of those alive today unless current habits are changed. Smoking causes 90 per cent of lung cancers. It can also cause cancer in a number of other parts of the body, including the mouth, pharynx, larynx, oesophagus, pancreas, renal pelvis, bladder, and cervix. There can be no doubt that giving up smoking brings down the risk. If a person manages to give up smoking before developing cancer or some other serious disease, most of the risk of dying from smoking-related diseases may be avoided. After ten years the risk will be more than halfway towards that of someone who has never smoked.
Diet - Diet is probably linked to about 30 to 35 per cent of cancers. Many researchers believe that it plays a part in many of the most common cancers, such as those of the breast and bowel. However, as yet, there is no concrete proof of which elements can cause cancer and which help to protect against it. At the moment, evidence suggests a protective role for fruit, vegetables, dietary fibre, and certain vitamins. Other factors, such as a high-fat or excessive meat diet, are thought to increase risk. For instance, many researchers think that an increased intake of fresh fruit and vegetables decreases the risk of stomach cancer. People who eat moderate amounts of fruit, such as one piece of fruit per day, have a substantially lower risk of developing this cancer.
Hormones - Hormones are proteins that are produced by a variety of special glands in the body, known as endocrine glands. They are secreted into and carried by the blood to their destinations known as target organs. There is no real evidence to suggest that hormones initiate the cancer process but there is no doubt that in certain circumstances. When a cancer is either establishing itself or is rapidly increasing in size, they can encourage the cancerous cells to grow at a greater rate. Such cancers are referred to as being hormone dependent. In the cancer of the male prostate gland however an artificially manufactured drug called stilboestrol which is chemically similar to the hormone oestrogen can actually cause a regression of prostatic cancer. In pregnancy existing cancers of the breast and cervix can be worsened due to certain hormonal levels that accompany pregnancy.
Radiation and Radon - As well as being a successful treatment for cancer, radiation can cause cancer. The risk from radiation is related directly to the dose received, and therefore for most people the amount received in a lifetime is relatively small. People who live in areas with high levels of radon, a radioactive gas, are more at risk of developing lung cancer.
Sunlight - Ultraviolet radiation (UV) types A and B from sunlight are responsible for most skin cancers.
Chemicals - Certain occupations carry an increased risk of cancer because workers are exposed to hazardous substances such as chemicals, asbestos, or radiation. It is therefore very important for work safety procedures to be put in place, to provide as much protection for workers as possible, and for workers to follow the guidelines.
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