Cancer
Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these cells to invade other tissues, either by direct growth into adjacent tissue through invasion or by implantation into distant sites by metastasis (in which cancer cells are transported through the blood or lymphatic system). Cancer may affect people at all ages, but risk increases with age. It is one of the leading causes of death in developed countries.
There are many types of cancer. Severity of symptoms depends on the site and character of the malignancy and whether there is metastasis. A definitive diagnosis usually requires the histologic examination of tissue by a pathologist. This tissue is obtained by biopsy or surgery. Most cancers can be treated and some cured, depending on the specific type, location, and stage.
Once diagnosed, cancer is usually treated with a combination of surgery, chemotherapy and radiotherapy. As research develops, treatments are becoming more specific for the type of cancer pathology. Drugs that target specific cancers already exist for many cancers. If untreated, cancers may eventually cause illness and death, though this is not always the case.
The unregulated growth that characterizes cancer is caused by damage to DNA, resulting in mutations to genes that encode for proteins controlling cell division. Many mutation events may be required to transform a normal cell into a malignant cell. These mutations can be caused by chemicals or physical agents called carcinogens, by close exposure to radioactive materials, or by certain viruses that can insert their DNA into the human genome. Mutations occur spontaneously, or are passed down generations as a result of germ line mutations.
Many forms of cancer are associated with exposure to environmental factors such as tobacco smoke, radiation, alcohol and certain viruses. While some of these can be avoided, there is no known way to entirely avoid the disease, and public health and vaccination programs are also important on a global scale.
Today, carcinoma is the medical term for a malignant tumor derived from epithelial cells. It is Celsus who translated carcinos into the Latin cancer, also meaning crab. Galen used "oncos" to describe all tumours, the root for the modern word oncology.
Hippocrates described several kinds of cancers. He called benign tumours oncos, Greek for swelling, and malignant tumours carcinos, Greek for crab or crayfish. This strange choice of name probably comes from the appearance of the cut surface of a solid malignant tumour, with a roundish hard center surrounded by pointy projections, vaguely resembling the silhouette of a crab.
He later added the suffix -oma, Greek for swelling, giving the name carcinoma. Since it was against Greek tradition to open the body, Hippocrates only described and made drawings of outwardly visible tumors on the skin, nose, and breasts. Treatment was based on the humor theory of four bodily fluids (black and yellow bile, blood, and phlegm).
According to the patient's humor, treatment consisted of diet, blood-letting, and/or laxatives. Through the centuries it was discovered that cancer could occur anywhere in the body, but humor-theory based treatment remained popular until the 19th century with the discovery of cells.
Though treatment remained the same, in the 16th and 17th centuries it became more acceptable for doctors to dissect bodies to discover the cause of death. The German professor Wilhelm Fabry believed that breast cancer was caused by a milk clot in a mammary duct. The Dutch professor Francois de la Boe Sylvius, a follower of Descartes, believed that all disease was the outcome of chemical processes, and that acidic lymph fluid was the cause of cancer.
His contemporary Nicolaes Tulp believed that cancer was a poison that slowly spreads, and concluded that it was contagious.
With the widespread use of the microscope in the 18th century, it was discovered that the 'cancer poison' spread from the primary tumor through the lymph nodes to other sites ("metastasis").
The use of surgery to treat cancer had poor results due to problems with hygiene.
The renowned Scottish surgeon Alexander Monro (1697-1767) saw only 2 breast tumor patients out of 60 surviving surgery for two years. In the 19th century, asepsis improved surgical hygiene and the survival statistics went up.
The idea that the body was made up of various tissues, that in turn were made up of millions of cells, laid rest the humor-theories about chemical imbalances in the body. The age of cellular pathology was born.
The first cause of cancer was identified through the work of British surgeon Percivall Pott, who discovered in 1775 that cancer of the scrotum was a common disease among chimney sweeps.
In the late 1800's, William Coley discovered that the rate of cure after surgery had been higher in the 18th century than in his day, when antiseptics were used to prevent infection.
This prompted him to develop a treatment based on injecting bacteria directly into a tumor. This elicited tumour shrinkage in some cases, probably by stimulating a non-specific immune reaction. Whilst Coley's Toxins fell out of use, there is currently interest in utilisation of non-specific immunity in the treatment of some cancers.
When Marie Curie and Pierre Curie discovered radiation, the first effective non-surgical cancer treatment became popular. In the first half of the 20th century, studies led to the introduction of chemotherapy.
Childhood leukemia cell culprit discovered BBC - January 17, 2008
Cancer's ethnic divide? BBC - January 17, 2008
New research suggests that black women tend to develop breast cancer
earlier than their white counterparts, and that the tumours in question
may even be biologically different from those of white women.
Multiple Skin Cancer Risk Behaviors Are Common Among US Adult Science Daily - January 11, 2008
Genome study finds 100 new cancer genes Guardian - March 7, 2007
Many gene mutations drive cancer BBC - March 7, 2007
Experts crack cancer 'gene codes' BBC - October 30, 2006
New Breast Cancer Gene Found Live Science - October 9, 2006
Gene therapy rids men of cancer BBC - September 2, 2006
US approves cervical cancer drug BBC - June 9, 2006
Cancer scientists find worm link BBC - June 2, 2006
Cancer scientists find worm link BBC - June 2, 2006
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