Overview, Causes, & Risk Factors

A cancer is a group of abnormal cells, known as a tumor, that grows uncontrollably. Cancerous tumors invade and destroy surrounding tissue. Not all tumors are cancerous. Benign tumors, which are not cancerous, do not invade and destroy tissue. However, a benign tumor may grow very large. Cancerous tumors may shed cancer cells that spread to other parts of the body. This is called a metastasis. Benign tumors do not spread in this way.

What is going on in the body?

A chromosome is genetic material within the nucleus of a cell. Chromosomes provide the so-called blueprints that direct normal cell function. The nucleus that houses the chromosomes is the control center for the cell. The nucleus of a normal cell, such as a muscle cell, controls its activity as part of a larger tissue, a muscle. The cell will then act in concert with other cells of that muscle to expand and contract, causing motion. Damage to the nucleus prevents the cell from behaving normally.

Cancer occurs when the damage causes changes that make the cell grow and divide wildly. When a cell becomes cancerous, over time a tumor forms from these abnormal cells. Because the tumor is made up of defective cells, it cannot function as it should. The body suffers in two ways:

A cancer is named by the type of organ tissue from which it developed. For example, breast cancer will always be called breast cancer, even if it spreads to other body parts. The type of tissue within an organ that underwent the cancerous change also further identifies a cancer. For example, lung cancer is grouped into several groups depending on exactly what kind of lung tissue was affected. A cancerous tumor does not grow any faster than the kind of tissue from which it started. But it does keep growing and multiplying uncontrollably. Healthy tissue does not grow constantly.

In the early stages of any cancer, you may not be able to see much of an effect on the body. But cancer cells can break off from the main tumor and travel through your blood stream to other parts of your body. These cancer cells may then form new tumors, known as metastases. As the cancer grows and spreads, or metastasizes, the person will likely begin to weaken. Cancer makes it hard for your body to function normally.

In the advanced stages of cancer, symptoms such as weight loss, weakness, and fatigue are common. At the same time, new cancerous tumors that spread to other parts of the body may cause other organs to fail. If not successfully treated, the cancer will destroy the functioning of vital body systems. This can lead to death.

These vital body functions include:

Most cancers occur in people older than age 55. This may be because cells become more vulnerable to damage after years of use. It is possible for children to have cancer, but this is rare. More men than women have cancer. The most common cause of cancer death in men and women is lung cancer.

What are the causes and risks of the disease?

For cancer to occur, something must damage the nucleus of the cell. Some people are born with a tendency for cancer. Their cells may be more vulnerable to the kind of damage that leads to cancer. For others, the damage occurs after years of exposure to substances that can cause cancer. Tobacco from any source is very dangerous. Certain chemicals, unprotected sun exposure, and radiation can all cause serious damage.

Symptoms & Signs

What are the signs and symptoms of the disease?

The specific symptoms of cancer depend upon where the cancer is located. In some cases, a tumor can stay hidden for years because it causes no damage to tissues that would result in an observable symptom. Examples of cancers that may stay hidden for a long time include the following.

Many times the symptoms of cancer are vague or can be mistaken for other diseases. The non-specific symptoms of cancer can include:

Any of these symptoms should prompt you to see your doctor.

Diagnosis & Tests

How is the disease diagnosed?

If cancer is suspected, it must be confirmed by examining the abnormal tissue in the pathology laboratory. This can mean removing a piece of the tissue with a biopsy. Sometimes the whole tumor is removed, which is known as a resection. Additional studies such as special X-rays and blood tests may be done to measure the extent of the disease. This is known as staging the disease.

Prevention & Expectations

What can be done to prevent the disease?

Cancer found while it is still in the early stages is much easier to treat. You can take the following cancer prevention steps.

Since some cancers cannot be prevented, early detection and diagnosis are key tools in improving cancer survival.

What are the long-term effects of the disease?

Half of all people with cancer are cured with treatment. And luckily, cancer can often be successfully controlled even if it is not cured. But, if cancer is not successfully treated, it will be fatal.

What are the risks to others?

There is no risk to others from people with cancer. Cancer cannot be spread from one person to another.

Treatment & Monitoring

What are the treatments for the disease?

Curing or controlling cancer may require that you use many forms of treatment. Some of these are listed below.

Surgery. The first treatment for many cancers is surgery to remove the solid tumor. If the tumor is small enough, the cancer can often be cured this way. This is a local treatment, and it is not effective for cancers that have spread to other parts of the body. Leukemia and lymphoma are not localized because they affect the blood system. So they also cannot be treated by surgery.

Chemotherapy.This is a type of treatment that involves the use of medicines. Your doctor gives these medicines to you either by mouth or directly into a vein. Next, they travel through your body via your blood. This is called a systemic treatment because the medicines may affect your whole body. This approach has been used to cure or control cancers such as leukemia that are more widespread than local. Or it may be used for cancers that were local, but have now spread to other parts of your body. Just as some infections do not respond to antibiotics, not all cancers respond to chemotherapy.

Radiation.In this local treatment, focused energy waves of radiation are directed at tumors. This can kill or slow the growth of many cancers. Cancers that are localized and sensitive to radiation may even be cured by this treatment. Examples of cancers that can be cured by radiation are Hodgkin disease and cancer of the voice box, or larynx.

Immunotherapy.This form of treatment uses the body's immune response to kill or control the cancer. It has only limited effectiveness. It is useful only for certain cancers. Many cancers are too advanced at diagnosis to be affected by this approach alone.

In many cases, a combination of treatments has proven most effective.

What are the side effects of the treatments?

The side effects depend on the type of treatment and the extent of treatment.

What happens after treatment for the disease?

After treatment, the person with cancer will be watched closely to determine the effectiveness of treatment. People who are cured of their cancers should be able to resume normal lives. If the treatment is not effective, other therapy may be tried. If all therapy has proved ineffective, every effort will be made to assure comfort during the final stages.

How is the disease monitored?

Each cancer is followed according to type and how it was diagnosed. Leukemia is followed by examining blood samples. Lung cancer is followed with special X-rays of the chest. Progression of an advancing cancer may be monitored through X-rays, depending where the cancer has spread or is suspected to have spread. Always report any new or worsening symptoms to your doctor.