Cancer
An excerpt from "Mayo Clinic A to Z Health Guide"
What is it?
Cancer refers to any one of a large number of diseases characterized by the development of cells that divide uncontrollably and have the ability to infiltrate and destroy body tissue. Cancer that starts in one part of the body has the ability to spread throughout the body.
What's the cause? Cancer is caused by changes (mutations) to the DNA within cells. Each cell's DNA contains a set of instructions telling it how to grow and divide. Errors in these instructions can allow a cell to become cancerous.
Most commonly, a gene mutation may instruct a healthy cell to do one of the following:
- Grow too fast. The cell grows and divides more rapidly than it should. This creates many new cells that have the same mutation.
- Forget to apply the brakes. Healthy cells know when to stop growing. Cancer cells lose such control. They continue to grow and accumulate.
- Overlook DNA errors. Specialized genes called repair genes look for errors in a cell's DNA and make corrections. A mutation in a repair gene may prevent an error from being corrected.
Risk factors
Some gene mutations are inherited but most occur after you're born. A number of factors can produce gene mutations and lead to cancer. They include the following:
- Age. Because cancer can take decades to develop, it's most common in people age 65 and older. However, it can occur at any age.
- Habits. Certain lifestyle choices are known to increase your risk of cancer. Smoking, excessive alcohol use, excessive exposure to the sun, lack of exercise, and having unsafe sex can contribute to cancer.
- Family history. Only a small portion of cancers are inherited. Having an inherited genetic mutation increases your risk but doesn't necessarily mean you'll get cancer.
- Health. Some chronic conditions can markedly increase your risk of developing certain cancers. Ulcerative colitis, for example, significantly increases the risk of colon cancer.
- Environment. Harmful chemicals in the environment can increase the risk of cancer. Examples include secondhand smoke or chemicals such as asbestos and benzene.
Symptom checker: Signs and symptoms associated with cancer vary depending on what part of the body is affected.
Some general signs and symptoms include:
- Fatigue
- Lump or area of thickening that can be felt under the skin
- Weight changes, including unintended loss or gain
- Skin changes, such as yellowing, darkening or redness of the skin, sores that won't heal, or changes to existing moles
- Changes in bowel or bladder habits
- Persistent cough
- Difficulty swallowing or hoarseness
- Persistent indigestion or discomfort after eating
- Persistent, unexplained muscle or joint pain
- Persistent, unexplained fevers or night sweats
What tests to expect
Cancer is most often diagnosed using a combination of these approaches:
Physical exam
During a physical exam, your health care provider may feel areas of your body for lumps that may indicate a tumor. Your provider may also look for changes in skin color or enlargement of an organ.
Laboratory tests
Laboratory tests, such as urine and blood tests, may help your health care provider identify changes associated with cancer. For instance, in people with leukemia, a common blood test called a complete blood count (CBC) may reveal an unusual number of white blood cells.
Imaging tests
Imaging tests used in diagnosing cancer may include a computerized tomography (CT) scan, bone scan, magnetic resonance imaging (MRI), ultrasound and X-ray, among others. These tests can identify tumors and other changes associated with cancer.
Biopsy
In a biopsy, a sample of cells are collected for testing in a laboratory. There are several ways of doing this, depending on the type of cancer and its location. In most cases, a biopsy is the only way to definitively diagnose cancer. Under a microscope, cancer cells look less orderly than other cells, with varying sizes and shapes.
Treatment
Health care providers have many tools when it comes to treating cancer. Treatment depends, in part, on the cancer itself.
Types
Treatments options include:
Surgery. The goal is to remove the cancer or as much of it as possible.Often, you'll have other treatments after surgery.
Chemotherapy. Chemotherapy uses medications to kill cancer cells. There are many chemotherapy drugs. Certain drugs are more effective for certain cancers.
Radiation therapy. Radiation therapy involves the use of high-powered energy beams, such as X-rays, to kill cancer cells.
Stem cell transplant. Also known as bone marrow transplant, this procedure involves transplanting your own stem cells or stem cells from a donor into your bone marrow. This is done to replenish the marrow and encourage the growth of healthy new blood cells after cancerous cells are destroyed by chemotherapy.
Immunotherapy. This treatment, also called biological therapy, uses the body’s immune system to fight cancer. It helps your immune system “see” the cancer and attack it.
Hormone therapy. Some types of cancer, such as breast and prostate cancers, are fueled by hormones. Removing those hormones or blocking their effects may cause the cancer cells to stop growing.
Targeted drug therapy. Targeted drug treatments focus on specific characteristics within cancer cells. For example, one type of targeted therapy stops the formation of new blood vessels, cutting off blood supply to the tumor. Another type blocks an enzyme that plays a role in the growth of cancer cells.
Other treatments may be available, depending on the type of cancer.
Lifestyle
There's no certain way to prevent cancer, but there are things you can do to reduce your risk:
