Cancer is one of the most common causes of death around the world. It causes about 12.5% (or one out of every eight) of all deaths worldwide, according to the World Health Organization.
Different types of cancer have different causes. Some things are known to cause cancer in a specific body part; other things are known to be able to cause many different types of cancer. For example, using tobacco (smoked or smokeless) can cause many types of cancers, such as lung, mouth, tongue, and throat cancers. Other things that are known to be able to cause cancer - or make a person more likely to get cancer - include: radiation including sunlight and X-rays in large or many doses, and exposure to radiation (for example in a nuclear power plant); chemicals and materials used in building and manufacturing (for example, asbestos and benzene); high-fat or low-fiber diets; air and water pollution; eating very little fruits and vegetables; obesity; not enough physical activity; drinking too much alcohol; and certain chemicals commonly used at home. Some cancers can also be caused by viruses. Many people who are exposed to these things do get cancer - but some do not.
There are many different kinds of cancers. Some of the most common are:
There is no sure cure for cancer. It can only be cured if all of the cancerous cells are cut out or killed in place. This means that the earlier the cancer is treated, the better the chances are for a cure (because the cancer cells may not have had enough time to copy themselves and spread so much that the person cannot be cured).
There are a few different types of treatments that are used to try to kill cancer cells. These treatments are:
There are a few reasons why treating cancer is complicated. For example:
Many, many people in many countries study cancer and work on finding treatments. There has been some good progress in finding treatments, and many cancers are treated with success. Along with looking for different medical treatments to treat cancer, some studies also look for things that people with cancer can do themselves to try to make themselves healthier. For example, one study showed that if a person with lymphedema (a swelling of the arm linked to breast cancer) lifts weights, he may be able to fight his cancer better than somebody who does not lift weights.
Cancer has been around for many thousands of years. Today, a lot of the medical terms used to describe cancer come from ancient Greek and Latin. For example, the Latinized Greek word carcinoma is used to describe a malignant tumor - a tumor made up of cancer cells. The Greeks also used the word "karkinos", which would be translated by Aulus Cornelius Celsus into the Latin word "cancer". The prefix 'carcino' is still used in medical words like carcinoma and carcinogenic. A famous Greek doctor, Galen, helped create another word that is very important to medicine today by using the word ""onkos"" to describe "all" tumours. This is where the word oncology, the branch of medicine that deals with cancer, comes from.
Hippocrates (a very famous ancient doctor who is often called the father of modern medicine) named many kinds of cancer. He called benign tumours (tumors that are not made up of cancer cells) "oncos". In Greek, "onkos" means 'swelling'. He called malignant tumours "karkinos". This means crab or crayfish in Greek. He used this term because he thought that if a solid malignant tumor was cut into, its veins looked like a crab: "the veins stretched on all sides as the animal the crab has its feet, whence it derives (gets) its name". Hippocrates later added "-oma" (Greek for 'swelling') after the word 'carcinos'. This is how the word "carcinoma" came about.
Because the ancient Greeks did not believe in opening up dead bodies to study them, Hippocrates was only able to describe and make drawings of tumors he saw from the outside of the body. He drew tumors that had been on the skin, nose, and breasts.
Hippocrates and other doctors at that time treated people based on the humor theory. This theory said that there were four types of fluid in the body (black, yellow bile, blood, and phlegm). Doctors tried to figure out whether these four "humors" (or body fluids) were in balance. They would then use treatments like blood-letting (cutting the patient and letting him bleed so that he would lose blood); laxatives (giving the patient foods or herbs to make him go to the bathroom), and/or changing the patient's diet. The doctors thought that these treatments would work to get the patient's four humors back into the right balance. The humor theory treatment was popular until the 19th century (the 1800s), when cells were discovered. By this time, people had realized that cancer can happen anywhere in the body.
The oldest known document that talks about cancer was discovered in Egypt and is thought to be from about 1600 B.C. The document talks about using surgery to treat eight cases of ulcers of the breast. These were treated by cauterization - by burning them - using a tool called "the fire drill". The document also says about cancer, "There is no treatment".
Another very early type of surgery used to treat cancer was written about in the 1020s. In "The Canon of Medicine", Avicenna (Ibn Sina) said that treatment should involve cutting out all diseased tissue. This included the use of amputation (removing a part of the body completely) or removing veins that ran in the direction of the tumor. Avicenna also suggested that the area that had been treated should be cauterized (or burned) if needed.
In the 16th and 17th centuries (the 1500s and 1600s), doctors started to be allowed to dissect bodies (or cut them open after death) in order to figure out the cause of death. Around this time, there were many different ideas about what caused cancer. The German professor Wilhelm Fabry believed that breast cancer was caused by a clot of milk in the part of a woman's breast that produces milk. The Dutch professor Francois de la Boe Sylvius believed that all disease was caused by chemical processes. He thought that cancer, in particular, was caused by acidic lymph. Nicolaes Tulp, who lived at the same time as Sylvius, believed that cancer was a poison that slowly spreads and was contagious.
A British surgeon named Percivall Pott was the first person to figure out one of the real causes of cancer. In 1775, he discovered that cancer of the scrotum was a common disease among chimney sweeps (people who cleaned out chimneys). Other doctors started studying this topic and coming up with other ideas about what causes cancer. Doctors then started working together and coming up with better ideas.
In the 18th century (the 1700s), many people started to use the microscope, and this made a big difference in helping doctors and scientists understand more about cancer. Using the microscope, scientists were able to see that the 'cancer poison' spread from one tumor through the lymph nodes to other sites ("metastasis"). This was first made clear by the English surgeon Campbell De Morgan, between 1871 and 1874.
Before the 19th century (the 1800s), using surgery to treat cancer usually had bad results. Doctors did not understand how important hygiene (or keeping things clean) is for preventing disease, especially after surgery. Because things were not kept clean during or after surgery, patients often got infections and died. For example, one well-known Scottish surgeon, Alexander Monro, kept records and found that 58 patients out of every 60 who had surgery for breast tumors died within the next two years.