What is Cancer? What Causes Cancer?

Cancer is a class of diseases characterized by out of control of cell growth. There are over 100 different types of cancer, and each is classified by the type of cell that is initially affected.
Cancer damages the body when damaged cells divide uncontrollably to form tumors or masses called tumors (except in the case of leukemia where the cancer prohibits normal function of blood through the abnormal cell division in the stream blood). Tumors can grow and interfere with the digestive, nervous and circulatory systems, and can release hormones that alter the function of the body. Tumors that are housed in one place and show limited growth is generally considered to be benign
More dangerous, or malignant tumors are formed when two things happen:
1. a cancer cell manages to move all the body systems using the blood or lymph, the destruction of healthy tissue in a process known as invasion
2. does the cell divide and grow, as new blood vessels to feed itself in a process called angiogenesis.
When a tumor spreads to other parts of successful and growing body, invading and destroying other tissues, is said to have metastasized. This same process is called metastasis, and the result is a serious condition that is very difficult to treat.
In 2007, cancer killed about 7.6 million people worldwide. Doctors and researchers who specialize in the study, diagnosis, treatment and prevention of cancer are called oncologists.

Genes - the DNA type
The cells may experience uncontrolled growth damage or mutations in DNA, and therefore, damage to genes involved in cell division. Four types of genes are responsible for cell division process: oncogenes tell cells when dividing, tumor suppressor genes tell cells when not to divide, suicide control and apoptosis genes tell the cell to kill themselves if something goes wrong, and DNA repair genes instruct the cell to repair damaged DNA.
Cancer occurs when cell mutations of genes that the cell can not correct the DNA damage and unable to commit suicide. Similarly, cancer is the result of mutations that inhibit the function of oncogenes and tumor suppressor genes, leading to uncontrolled cell growth.
Carcinogens
Carcinogens are a class of substances that are directly responsible for damage DNA, promote or assist cancer. The snuff, asbestos, arsenic, radiation, like gamma rays and X rays, the sun, and compounds in car exhaust fumes are examples of carcinogens. When our bodies are exposed to carcinogens, free radicals are formed to try to steal electrons from other molecules in the body. Theses free radicals damage cells and affect their ability to function normally.
Genes - the kind of family
The cancer may be the result of a genetic predisposition that is inherited from family members. It may be born with certain genetic mutations or a faulty gene that causes a statistically more likely to develop cancer in the future.
Other medical factors
As we age, there is an increase in the number of potential cancer-causing mutations in our DNA. This makes age an important risk factor for cancer. Several viruses have also been linked to cancer, such as human papillomavirus (a cause of cervical cancer), hepatitis B and C (causes liver cancer) and Epstein-Barr virus (a cause of some cancers of children). human immunodeficiency virus (HIV) - and all that suppresses or weakens the immune system - inhibits the body's ability to fight infection and increases the likelihood of developing cancer.