What is cancer?
         In simplest terms, cancer is a disease of the cells characterized by a change in basic cell behavior and structure and by the unrestricted growth and spread of the diseased cells. Since every living thing is made up of cells, cancer can affect plants and animals as well as human beings. And the discovery by paleontologists of cancerous cell formations in the bones of prehistoric dinosaurs points to the existence of the disease long before human beings ever appeared.
         Much has been learned about cell structure through the use of sophisticated instruments such as the electron microscope, which can magnify objects to over 100,000 times their original size. With the aid of such instruments, differences between normal and cancerous cells have been observed in great detail.

The Cancerous Cell
         Cancer Cell Structure. Cells in the very early stages of cancer are usually similar in appearance to cells of normal tissue. As cancer progresses, however cell changes become more apparent. The extent of cell change in an abnormal cell varies according to the type of cancer involved: Highly malignant tissue may appear so different from normal tissue that it is difficult to tell where a cell from such tissue originated. 
         One striking characteristic of a cancer cell is chromosome abnormality. Instead of containing the normal forty-six chromosomes, a human cancer cell may contain double that number, or even several hundred chromosomes.

         Cancer Cell Division. In the cancer cell the mechanism that regulates cell growth, development, and differentiation breaks down. Cell growth is unregulated: Cells continue to divide even though they are not needed by the body. In most types of cancer this uncontrolled division of cells results in a mass or lump of excess tissue, known as a tumor. Not all tumors, however, are cancerous, or malignant; noncancerous tumors are said to be benign. Benign tumors are localized; they do not spread in the same way that malignant tumors do, and they rarely develop into malignancies. Warts and birthmarks are common benign tumors. Researchers believe that cancer cells develop gradually over a period of time. There is much evidence to indicate that a cancer that might eventually prove fatal can originate in a single malignant cell.

         Cancer Cell Movement. Cancer cells multiply at an abnormally high rate and possess the ability to spread to other parts of the body and invade healthy tissue. Cancer cells can travel all over the body, regardless of the tissue of their origin. Furthermore, the mechanism that tells the cell when to cease moving is faulty in a cancerous cell. When a cancer cell encounters other cells, contact inhibition is absent. Instead of attaching itself to a group of cells, the malignant cell invades and eventually overruns neighboring cell masses. Such growth is called invasion. 
         Cancer cells can easily become dislodged from one another and spread through the bloodstream or lymph system to other parts of the body. This spreading process is known as metastasis, and the new colonies are called metastases. 
         A third pattern of cancer cell behavior is manifested in cancer involving the body cavities. Malignant tissues may spread by a process called implantation, or diffusion, in which poorly adhering cancer cells slough off of a tumor and lodge in nearby organs, where new cancerous growths develop.
         The two characteristics of cancer cells their rapid division and their ability to spread throughout the body account for the high fatality rate of cancer. The multiplying cancer cells demand the nutrients and the space that would otherwise go to normal cells. Normal tissue is starved and squeezed out. Furthermore, the presence of cancer cells throughout the body interferes in some way with the body's blood-producing organs. Red and white blood cells and platelets arc produced in insufficient quantities, leading to severe anemia, repeated infection, and internal bleeding.

Protect Yourself Against Cancer
• Don't use tobacco. Quitting smoking is the best way to prevent lung cancer as well as several other serious diseases. Avoiding all forms of smokeless tobacco is the best way to prevent cancers of the mouth, throat, larynx, and esophagus.

• Watch your diet. Keep the number of high-fat foods to an absolute minimum; instead, increase the amount of foods rich in fiber and in vitamins A and C.

• Don't over sun. Sunbath in small doses, especially if you have a fair complexion. If you have to be out in the sun a lot, cover up sensibly and use sunscreen lotions to help prevent skin cancer.

• Don't abuse alcohol. If you are a heavy drinker, you are at risk for cancers of the mouth, throat, larynx, esophagus, and liver; you increase this risk greatly if you also use tobacco.

• If you are a woman, do breast self-examination.
By examining your breasts every month, you will be able to spot any developing tumor in time for it to be treated successfully.

• Have a colorectal examination. If you are age 40 or over, have a digital rectal exam every year; if you are over 50, have a blood stool test every year in addition, and a full proctoscopic exam every three to five years.

• Get a Pap test. Have a Pap test every three years (after two initial negative tests) to protect yourself against cervical cancer.

• Have an oral exam. Your dentist or physician can easily recognize the early symptoms of mouth cancer. Schedule visits regularly.

• Get a complete checkup. A regular physical examination should include examinations for cancers of the thyroid, testes, prostate, mouth, ovaries, skin, and lymph nodes. Women between 20 and 40 should have a full pelvic exam every three years; women over 40 should have one every year. Men over 40 should have a prostate exam every year.