Cancerous cells avoid
apoptosis, which kills damaged
cells.

Cancer is a class of diseases characterized by malignant neoplasia, which translates approximately to "bad new growth." What this means is that, when cells mutate and begin to grow our of control or when cells fail to die normally, they build up into the "bad new growth," or a neoplasm. These neoplasic build-ups are known as tumors.

Cancer is caused by a series of mutations in genes that control cells' ability to grow and multiply. Some mutations are inherited genetically, some are from environmental factors (smoking, radiation poisoning, etc.). These mutations cause cells to multiply vigorously or lose their ability to die normally.

There are more than 100 different kinds of cancer, as cancer can arise anywhere in your body. There are carcinomas, the most common type of cancer, which originate in tissues that cover a surface or line a cavity of the body. There are sarcomas, which begin in tissues that connect, support, or surround other tissues. Lymphomas are cancers of the lymphatic system, which is the bodily system that cleanses cells. Then, there are Leukemias, or cancers related to the blood. There are also brain cancers and skin cancers (like melanomas).

Cancer is called metastatic if it spreads to other parts of the body through the blood or lymph system, creating secondary neoplasms. If, for example, lung cancer spreads to the liver, the chances of "beating" the cancer become much slimmer, as the cancer has entered either the bloodstream or the lymph nodes and will probably be circulating in your body forever, except in very rare, but very moving miracles.

Cancer attacks one out of every two men and one out of every three women in the United States at some point in their lives. There are almost 1.5 million cases of caner diagnosed in the U.S. alone every year. 560,000 people in the U.S. die of cancer annually, making it the second leading cause of death (second only to heart disease).