Cancer Health Article

Cancer

Cancer is a disease characterized by the uncontrolled growth and spread of abnormal cells. Around the world, over 10 million cancer cases occur annually. Half of all men and one-third of all women in the United States will develop some form of cancer during their lifetime. It is one of the most feared diseases, primarily because half of those diagnosed with cancer in the United States will die from it. Cancer is a leading cause of death around the world, causing over 6 million deaths a year. The exact causes of most types of cancer are still not known, and there is not yet a cure for cancer. However, it is now known that the risk of developing many types of cancer can be reduced by adopting certain lifestyle changes, such as quitting smoking and eating a better diet.

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.

Types of Cancer

Cancers are classified according to the types of cells in which they develop. Most human cancers are carcinomas, which arise from the epithelial cells that form the superficial layer of the skin and some internal organs. Leukemias affect the blood and blood-forming organs such as bone marrow, the lymphatic system, and the spleen. Lymphomas affect the immune system. Sarcoma is a general term for any cancer arising from muscle cells or connective tissues.

Growth and Spread of Cancer

Cancer develops when cells in a particular part of the body begin to grow out of control. Normal body cells grow, divide, and die in an orderly way. Cancer cells, however, continue to grow and divide without dying. Instead, they outlive normal cells and continue to form new abnormal cancer cells. As most cancer cells continue to grow, they lump together and form an extra mass of tissue. This mass is called a malignant tumor.

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.