Defining Cancer
Cancer is a term used for diseases in which abnormal cells divide without control and are able to invade other tissues. Cancer cells can spread to other parts of the body through the blood and lymph systems.
Cancer is not just one disease but many diseases. There are more than 100 different types of cancer. Most cancers are named for the organ or type of cell in which they start - for example, cancer that begins in the colon is called colon cancer; cancer that begins in basal cells of the skin is called basal cell carcinoma.
Prevalence
Cancer is, in general, more common in industrialized nations, but there has been a growth in cancer rates in developing countries, particularly as these nations adopt the diet and lifestyle habits of industrialized countries. Over one million people in the United States get cancer each year. Anyone can get cancer at any age; however, about 80 percent of all cancers occur in people over the age of fifty-five.
Cancer can affect any site in the body. About one hundred human cancers are recognized. The four most common cancers in the United States are: lung, colon/rectum, breast, and prostate . Together, these cancers account for over 50 percent of total cancer cases in the United States each year.
There is a marked variation among countries in incidence of different cancers. Most of the variation in cancer risk among populations, and among individuals, is due to environmental factors, such as cigarette smoking and certain dietary patterns, that can affect one's risk of developing cancer. For example, individuals living in Australia have the highest worldwide lifetime risk of skin cancer, at over 20 percent, due to the high level of exposure to the sun of people in Australia. People in India have twenty-five times the average risk of developing oral cancer sometime during their lives due to the popularity of chewing tobacco in that country. In fact, India has the world's highest incidence of oral cancer, with 75,000 to 80,000 new cases a year. The population of Japan has the highest rates of stomach cancer in the world due to the high consumption of raw fish by the Japanese.
Cancer types can be grouped into broader categories. The main categories of cancer include:
*Carcinoma - cancer that begins in the skin or in tissues that line or cover internal organs.
*Sarcoma - cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue.
*Leukemia - cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood.
*Lymphoma and myeloma - cancers that begin in the cells of the immune system.
*Central nervous system cancers - cancers that begin in the tissues of the brain and spinal cord.
-Origins of Cancer:
All cancers begin in cells, the body's basic unit of life. To understand cancer, it's helpful to know what happens when normal cells become cancer cells.
The body is made up of many types of cells. These cells grow and divide in a controlled way to produce more cells as they are needed to keep the body healthy. When cells become old or damaged, they die and are replaced with new cells.
However, sometimes this orderly process goes wrong. The genetic material (DNA) of a cell can become damaged or changed, producing mutations that affect normal cell growth and division. When this happens, cells do not die when they should and new cells form when the body does not need them. The extra cells may form a mass of tissue called a tumor.
Not all tumors are cancerous; tumors can be benign or malignant.
*Benign tumors aren't cancerous. They can often be removed, and, in most cases, they do not come back. Cells in benign tumors do not spread to other parts of the body.
*Malignant tumors are cancerous. Cells in these tumors can invade nearby tissues and spread to other parts of the body. The spread of cancer from one part of the body to another is called metastasis.
Some cancers do not form tumors. For example, leukemia is a cancer of the bone marrow and blood.
Let's Know More About Cancer
Growth and Spread of Cancer :
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| the division of cancer cells (left and right) and two healthy white blood cells (above and below). In normal cells, cell division is balanced by cell death, but cancerous cells continue to divide and accumulate, damaging nearby tissues. |
As a malignant tumor grows, it damages nearby tissue. Some cancers, like leukemia, do not form tumors. Instead, these cancer cells involve the blood and blood-forming organs and circulate through other tissues, where they grow.
Cancer can begin in one part of the body and spread to others. The spread of a tumor to a new site is called metastasis. This process occurs as cancer cells break away from a tumor and travel through the bloodstream or the lymph system to other areas of the body. Once in a new location, cancer cells continue to grow out of control and form a new malignant tumor.
And Now , We will see How Cancer Growth
*Causes of Cancer:
The exact cause of cancer is not known. Most cancers result from permanent damage to genes or from mutations, which occur either due to internal factors, such as hormones , immune conditions, metabolism , and the digestion of nutrients within cells, or by exposure to environmental or external factors. A chemical or other environmental agent that produces cancer is called a carcinogen.
Also Cancer can be caused by factors such as:
*Aging : Old age causes a significant increase in the probability of cancer since most cancers occur above the age of 65. However, cancer can occur at any age as well.
*Tobacco use : Tobacco is one of the most common and preventable factors in cancer-related deaths. It accounts for more than 180,000 deaths in the US every year.*Sunlight : The Sun emits many types of harmful radiation but Ultra Violet radiation is the most dangerous in terms causing Cancer. It causes degeneration of the skin which leads to skin cancer.
*Radiation : Apart from sun’s radiation, there are other sources of radiation on earth, including ionizing radiation, radioactive fallout, Radon gas and X rays. Ionizing radiation is caused by rays entering from outer space. Radioactive fallout occurs due to accidents at Nuclear plants or while testing atomic weapons. Radon gas is found in rocks and earth and is the primary cause of Cancer in miners. X rays are used in medical procedures so are not extremely harmful if exposed with appropriate measures.
*Chemical industry : There are several other chemicals found in the paint industry or construction work which can also lead to Cancer.*Viruses : Certain viruses and bacteria can also be the cause of Cancer.
Hormone supplements : Certain hormone supplements prescribed by doctors, such as estrogen and progestin, can have significant side effects which may lead to Cancer.
*Family history : Not all but certain types of Cancer can be passed on through genes and may affect multiple generations. These include melanoma (skin cancer) and cancers of the breast, ovary, colon and prostate.
*Alcohol consumption : Having large amounts of Alcohol can also lead to Cancer.
*Health imbalance : Poor diet or being overweight can also be the cause of Cancer.
These are not the only causes of Cancer however, but they are the primary reasons and people who have them or work in Cancer causing environments would be well-advised to consult a doctor.
Prevention :
All cancers caused by cigarette smoking and heavy use of alcohol could be prevented completely. Approximately 30 percent of all cancers worldwide are due to tobacco use. Many of the skin cancers could be prevented by protection from sunlight. Certain cancers that are related to infectious exposures, such as HBV, HPV, HIV, and Helicobacter could be prevented through behavioral changes, vaccines , or antibiotics . Research shows that about 30 to 40 percent of all cancers worldwide are due to dietary factors and lack of physical activity, including obesity, and could therefore have been prevented. By making changes in regard to diet, exercise, healthy weight maintenance, and tobacco use, the incidence of cancer around the world could be reduced by 60 to 70 percent
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