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Cancer (medicine)

There is also a constellation named Cancer: see Cancer (constellation).

In medicine, cancer is a general term for any of a number of different diseases where some of the body's own cells divide in an uncontrolled manner. The resulting new cells can form a malignant tumor (a neoplasm) or propagate throughout the body.

Cancers are capable of spreading through the body by two mechanisms: invasion and metastasis. Invasion refers to the direct migration and penetration by cancer cells into neighboring tissues. Metastasis refers to the ability of cancer cells to penetrate into lymphatic and blood vessels, circulate through the bloodstream, and then invade normal tissues elsewhere in the body. Cancer is most deadly when it metastasizes.

Cancer is, ultimately, a disease of genes. Typically, a series of several mutations is required before a cell becomes a cancer cell. We distinguish between oncogenes, which promote cancer when "switched on" by a mutation, and tumor suppressor genes, which prevent cancer unless "switched off" by a mutation. These mutations can have various causes: radiation or chemicals called carcinogens; some inherited predisposition is not uncommon; some viruses that can cause cancer have also been described. Usually, they carry in their genome some oncogene or tumor suppressor inactivating gene. In about 15% of all cancers, viruses seem to play a role. Finally, damage by free radicals, which are a natural by-product of oxygen metabolism, can cause mutations in the DNA. For most of the cancers, it cannot be told which event was the initial cause. However, with molecular biology it is possible to characterize the mutations within a tumor, and to a certain extent to predict its behavior. For example, about half of the tumors are deficient in the tumor suppressor gene p53, also known as "the guardian of the genome". This is associated with poor prospects for the patient, since those tumor cells are unlikely to go into apoptosis (programmed cell death) after they are damaged by therapy. There are more mutations that make a tumor more malignant. Telomerase mutations enable a tumor cell to divide indefinitely. Other mutations enable the tumor to grow new blood vessels to feed it, or to detach from the surrounding tissue, spreading to other parts of the body.

Cancer has become an important problem with the rise in life expectancy, as the above mentioned mutations become more likely the longer a person lives. Though great progress in treatment has been made, most cancers in advanced stages remain incurable and ultimately fatal. The field of medicine concerned with the treatment of cancer is oncology.

Treatment of cancer typically involves surgery to remove tumors and nearby lymph nodes to which the cancer may have spread, combined with radiation therapy and/or chemotherapy. The latter two target cells in the body that are rapidly dividing. This includes the cancer cells but also certain healthy ones, which is the reason for the severe side effects of these treatments.

Forms The term cancer is very broad and covers many different illnesses including:

Treatments

Cure for Cancer[?] Agencies Below is a list of some well-known institutions dedicated to funding cancer research[?] that would eventually lead to a cure for cancer.

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