Monday, 1 October 2012

Cancer History, origin of cancer, description of cancer


The History of Cancer 


The study of cancer, called oncology, is the work of countless doctors and scientists around the

world whose discoveries in anatomy, physiology, chemistry, epidemiology, and other related fields
made oncology what it is today. Technological advances and the ever-increasing understanding of
cancer make this field one of the most rapidly evolving areas of modern medicine.

What is cancer? 


Cancer begins when cells in a part of the body start to grow out of control. There are many kinds

of cancer, but they all start because of out-of-control growth of abnormal cells. To learn more
about how cancer forms and grows, see our document called What Is Cancer?
Cancer is the second leading cause of death in the United States. About one-half of all men and
one-third of all women in the US will develop cancer during their lifetimes. Today, millions of
people are living with cancer or have had cancer.

Oldest descriptions of cancer 


Human beings and other animals have had cancer throughout recorded history. So it’s no surprise

that from the dawn of history people have written about cancer. Some of the earliest evidence of
cancer is found among fossilized bone tumors, human mummies in ancient Egypt, and ancient
manuscripts. Growths suggestive of the bone cancer called osteosarcoma have been seen in
mummies. Bony skull destruction as seen in cancer of the head and neck has been found, too.
Our oldest description of cancer (although the word cancer was not used) was discovered in Egypt
and dates back to about 3000 BC. It is called the Edwin Smith Papyrus and is a copy of part of an
ancient Egyptian textbook on trauma surgery. It describes 8 cases of tumors or ulcers of the breast
that were treated by cauterization with a tool called the fire drill. The writing says about the
disease, “There is no treatment.”

Origin of the word cancer 


The origin of the word cancer is credited to the Greek physician Hippocrates (460-370 BC), who is

considered the “Father of Medicine.” Hippocrates used the terms carcinos and carcinoma to
describe non-ulcer forming and ulcer-forming tumors. In Greek, these words refer to a crab, most
likely applied to the disease because the finger-like spreading projections from a cancer called to
mind the shape of a crab. The Roman physician, Celsus (28-50 BC), later translated the Greek term
into cancer, the Latin word for crab. Galen (130-200 AD), another Roman physician, used the word oncos (Greek for swelling) to describe tumors. Although the crab analogy of Hippocrates and
Celsus is still used to describe malignant tumors, Galen’s term is now used as a part of the name
for cancer specialists — oncologists.

Sixteenth to eighteenth centuries 


During the Renaissance, beginning in the 15th century, scientists developed greater understanding

of the human body. Scientists like Galileo and Newton began to use the scientific method, which
later was used to study disease. Autopsies, done by Harvey (1628), led to an understanding of the
circulation of blood through the heart and body that had until then been a mystery.
In 1761, Giovanni Morgagni of Padua was the first to do something which has become routine
today — he did autopsies to relate the patient’s illness to pathologic findings after death. This laid
the foundation for scientific oncology, the study of cancer.
The famous Scottish surgeon John Hunter (1728−1793) suggested that some cancers might be
cured by surgery and described how the surgeon might decide which cancers to operate on. If the
tumor had not invaded nearby tissue and was “moveable,” he said, “There is no impropriety in
removing it.”
A century later the development of anesthesia allowed surgery to flourish and classic cancer
operations such as the radical mastectomy were developed.

Nineteenth century 


The 19th century saw the birth of scientific oncology with use of the modern microscope in

studying diseased tissues. Rudolf Virchow, often called the founder of cellular pathology, provided
the scientific basis for the modern pathologic study of cancer. As Morgagni had linked autopsy
findings seen with the unaided eye with the clinical course of illness, so Virchow correlated
microscopic pathology to illness.
This method not only allowed a better understanding of the damage cancer had done, but also
aided the development of cancer surgery. Body tissues removed by the surgeon could now be
examined and a precise diagnosis could be made. The pathologist could also tell the surgeon
whether the operation had completely removed the cancer.

Cancer causes: Theories throughout history 


From the earliest times, physicians have puzzled over the causes of cancer. Ancient Egyptians

blamed cancers on the gods.


Humoral theory 


Hippocrates believed that the body had 4 humors (body fluids): blood, phlegm, yellow bile, and

black bile. When the humors were balanced, a person was healthy. The belief was that too much or
too little of any of the humors caused disease. An excess of black bile in various body sites was
thought to cause cancer. This theory of cancer was passed on by the Romans and was embraced by
the influential doctor Galen’s medical teaching, which remained the unchallenged standard through the Middle Ages for over 1,300 years. During this period, the study of the body, including
autopsies, was prohibited for religious reasons, which limited progress of medical knowledge.

Lymph theory 


Among theories that replaced the humoral theory of cancer was the formation of cancer by another

body fluid, lymph. Life was believed to consist of continuous and appropriate movement of the
fluid parts of the body through the solid parts. Of all the fluids, the most important were blood and
lymph. Stahl and Hoffman theorized that cancer was composed of fermenting and degenerating
lymph, varying in density, acidity, and alkalinity. The lymph theory gained rapid support. John
Hunter, the Scottish surgeon from the 1700s, agreed that tumors grow from lymph constantly
thrown out by the blood.


Blastema theory 



In 1838, German pathologist Johannes Muller demonstrated that cancer is made up of cells and not

lymph, but he believed that cancer cells did not come from normal cells. Muller proposed that
cancer cells developed from budding elements (blastema) between normal tissues. His student,
Rudolph Virchow (1821−1902), the famous German pathologist, determined that all cells,
including cancer cells, are derived from other cells.

Chronic irritation theory 


Virchow proposed that chronic irritation was the cause of cancer, but he believed incorrectly that

cancers “spread like a liquid.” In the 1860s, German surgeon, Karl Thiersch, showed that cancers
metastasize through the spread of malignant cells and not through some unidentified fluid.

Trauma theory 


Despite advances in the understanding of cancer, from the late 1800s until the 1920s, trauma was

thought by some to cause cancer. This belief was maintained despite the failure of injury to cause
cancer in experimental animals.

Infectious disease theory 


Zacutus Lusitani (1575−1642) and Nicholas Tulp (1593−1674), 2 doctors in Holland, concluded at

almost the same time that cancer was contagious. They made this conclusion based on their
experiences with breast cancer in members of the same household. Lusitani and Tulp publicized
the contagion theory in 1649 and 1652, respectively. They proposed that cancer patients should be
isolated, preferably outside of cities and towns, in order to prevent the spread of cancer.
Throughout the 17th and 18th centuries, some believed that cancer was contagious. In fact, the first
cancer hospital in France was forced to move from the city in 1779 because people feared cancer
would spread throughout the city. Although human cancer, itself, is not contagious, we now know
that certain viruses, bacteria, and parasites can increase a person’s risk of developing cancer. Cancer epidemiology
During the 18th century, 3 important observations launched the field of cancer epidemiology
(epidemiology is the study of causes, distribution, and control of diseases):
• In 1713, Bernardino Ramazzini, an Italian doctor, reported the virtual absence of cervical
cancer and relatively high incidence of breast cancer in nuns and wondered if this was in some
way related to their celibate lifestyle. This observation was an important step toward
identifying and understanding the importance of hormones (like the changes that come with
pregnancy) and sexually-transmitted infections and cancer risk.
• In 1775, Percival Pott of Saint Bartholomew’s Hospital in London described an occupational
cancer in chimney sweeps, cancer of the scrotum, which was caused by soot collecting in the
skin folds of the scrotum. This research led to many more studies that identified a number of
occupational carcinogenic exposures and led to public health measures to reduce a person’s
cancer risk at work.
• Thomas Venner of London was one of the first to warn about tobacco dangers in his Via Recta,
published in London in 1620. He wrote that “immoderate use of tobacco hurts the brain and the
eye and induces trembling of the limbs and the heart.” And 150 years later, in 1761, only a few
decades after recreational tobacco became popular in London, John Hill wrote a book entitled
Cautions Against the Immoderate Use of Snuff. These first observations linking tobacco and
cancer led to epidemiologic research many years later (in the 1950s and early 1960s) which
showed that smoking causes lung cancer and led to the US Surgeon General’s 1964 report
Smoking and Health.
Epidemiologists continue to search for factors that cause cancer (like tobacco use, obesity,
ultraviolet radiation), as well as those things that can help protect against cancer (such as physical
activity and a healthy diet). This research provides evidence to guide public health
recommendations and regulations.
As molecular biologists learn more about how factors cause or prevent cancer, this information is
used to study molecular epidemiology, which is the study of interactions between genes and
external factors.
Modern knowledge and cancer causes


Viral and chemical carcinogens 



In 1915, Katsusaburo Yamagiwa and Koichi Ichikawa at Tokyo University, induced cancer in lab

animals for the first time by applying coal tar to rabbit skin. More than 150 years had passed since
clinician John Hill of London recognized tobacco as a carcinogen (a substance known or believed
to cause cancer in humans). Many more years passed before tobacco was “rediscovered” as the
most destructive source of chemical carcinogens known to man.
Today we recognize and avoid many specific substances that cause cancer: coal tars and their
derivatives (like benzene), some hydrocarbons, aniline (a substance used to make dyes), asbestos,
and many others. Ionizing radiation from a variety of sources, including the sun, is also known to
cause cancer. To ensure the public’s safety, the government has set safety standards for many substances, including benzene, asbestos, hydrocarbons in the air, arsenic in drinking water, and
radiation.
In 1911, Peyton Rous, at the Rockefeller Institute in New York, described a type of cancer
(sarcoma) in chickens caused by what later became known as the Rous sarcoma virus. He was
awarded the Nobel Prize for that work in 1968. Several viruses are now linked to cancer in
humans, including:
• Long-standing infection with the hepatitis B or C viruses can lead to cancer of the liver.
• One of the herpes viruses, the Epstein-Barr virus, causes infectious mononucleosis and has
been linked to non-Hodgkin lymphomas and nasopharyngeal cancer.
• People with human immunodeficiency virus (HIV) have greater increased risk of developing
several cancers, especially Kaposi sarcoma and non-Hodgkin lymphoma.
• Human papilloma viruses (HPVs) have been linked to many cancers, especially those of the
cervix, vulva, vagina, anus, and penis. Some head and neck cancers (mostly the tongue and
tonsils) are linked to the high-risk types of HPV, too. Today there is a vaccine to help prevent
HPV infection.
As of 2012, the World Health Organization’s International Agency for Research on Cancer
(IARC) has identified more than 100 chemical, physical, and biological carcinogens. Many of
these associations were recognized long before scientists understood much about how cancer
develops. Today, research is discovering new carcinogens, explaining how they cause cancer, and
providing insight into ways to prevent cancer.
By the middle of the 20th century, scientists had the instruments they needed to work on some of
the complex problems of chemistry and biology that remained unsolved. James Watson and
Francis Crick, who received a Nobel Prize in 1962 for their work, had discovered the exact
chemical structure of DNA, the basic material in genes.
DNA was found to be the basis of the genetic code that gives orders to all cells. After learning how
to translate this code, scientists were able to understand how genes worked and how they could be
damaged by mutations (changes or mistakes in genes). These modern techniques of chemistry and
biology answered many complex questions about cancer.
Scientists already knew that cancer could be caused by chemicals, radiation, and viruses, and that
sometimes cancer seemed to run in families. But as the understanding of DNA and genes
increased, they learned that it was the damage to DNA by chemicals and radiation, or the
introduction of new DNA sequences by viruses that often led to the development of cancer. It
became possible to pinpoint the exact site of the damage on a specific gene.
Scientists discovered that sometimes defective genes are inherited, and sometimes these inherited
genes are defective at the same points that chemicals exert their effect. In other words, most of the
things that caused cancer (carcinogens) caused genetic damage (mutations) that looked a lot like
the mutations that could be inherited and could result in the same types of cancer if more mutations
were introduced.

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