Cancer

Cancer is the name for a group of more than 100 related diseases. There are many kinds of cancer, but all cancers start when some of the body's cells grow out of control. Untreated cancers can cause serious illness and death.

Normal body cells grow, divide to make new cells, and die in an orderly way. Cancer starts when cells in a part of the body start to grow and divide uncontrollably. Cancer cell growth is different from normal cell growth. Instead of dying, cancer cells continue to grow and form new, abnormal cells. Cancer cells can also invade (grow into) other tissues, which normal cells cannot do. Growing out of control and invading other tissues are what makes a cell a cancer cell.

Changes to the microscopic, genetic parts of a cell - their deoxyribonucleic acid (DNA) – make cells become cancerous. DNA is in every cell and it directs all its actions. In a normal cell, when DNA is damaged the cell either repairs the damage or dies. In cancer cells, the damaged DNA is not repaired, but the cell still does not die like it should. Instead, the cell goes on making new cells that the body does not need or do not work properly. These new cells all have the same damaged DNA as the first cell does.

People can inherit abnormal or damaged DNA, but most DNA damage is caused by mistakes that happen while a normal cell is reproducing or by something in the environment. Sometimes DNA damage may be caused by exposure to something like cigarette smoking or sun exposure. Still, the exact cause of most cancers is unknown and most cancers are likely caused by a combination of factors.

In most cases, the cancer cells form a tumor or a solid mass. Over time, the tumors can invade nearby normal tissue, crowd it out, or push it aside. Some cancers, like leukemia, rarely form tumors. Instead, these cancer cells involve the blood and blood-forming organs and circulate through other tissues where they grow. Cancer cells often travel to other parts of the body where they can grow and form new tumors that crowd out normal tissue. This happens when the cancer cells get into the body’s bloodstream or lymph vessels. The process of cancer spreading is called metastasis.

No matter where a cancer may spread, it is always named for the place where it started. For instance, colon cancer that has spread to the liver is called metastatic colon cancer, not liver cancer.

Different types of cancer can behave very differently. The signs and symptoms of cancer and the treatment options depend on the type of cancer and how long it has been in your body. Most cancer treatments include surgery, radiation, and/or chemotherapy.

Cancer is the second-leading cause of death in the United States. Survival rates are improving for many types of cancer, thanks to improvements in cancer screening and cancer treatment.

Cancer is a complex group of diseases with many potential causes, including genetic factors; lifestyle factors such as tobacco use, diet, and physical activity; certain types of infections; and environmental exposures to different types of chemicals and radiation.

Essentially, cancer is a genetic disease: it is caused by changes to genes that control the way our cells function, especially how they grow and divide. Genetic changes that cause cancer can be inherited from our parents. They can also arise as a result of errors that occur as cells divide or because of damage to DNA caused by certain environmental exposures. Cancer-causing environmental exposures include substances, such as the chemicals in tobacco smoke, and radiation, such as ultraviolet rays from the sun.

Each person’s cancer has a unique combination of genetic changes. As the cancer continues to grow, additional changes will occur. Even within the same tumor, different cells may have different genetic changes.

The majority of cancers occur in people who do not have any known risk factors. Factors known to increase your risk of cancer include:

• Your age. Cancer usually takes decades to develop. Most people diagnosed with cancer are 65 or older, but cancer can be diagnosed at any age.
• Your habits. Smoking, drinking more than one alcoholic drink a day (for women of all ages and men older than age 65) or two drinks a day (for men age 65 and younger), excessive exposure to the sun or frequent blistering sunburns, being obese, and having unsafe sex can contribute to cancer.
• Your family history. Only a small portion of cancers are due to an inherited condition. If cancer is common in your family, it is possible that mutations are being passed from one generation to the next. In this case, genetic testing may be able to identify inherited mutations that might increase the risk of certain cancers.
• Your health conditions. Some chronic health conditions, such as ulcerative colitis, can increase your risk of developing certain cancers. Talk to your doctor about your risk.
• Your environment. The environment around you may contain harmful chemicals that can increase your risk of cancer. Even if you do not smoke, you might inhale secondhand smoke if you go where people are smoking or if you live with someone who smokes. Chemicals in your home or workplace, such as asbestos and benzene, also are associated with an increased risk of cancer.

See your doctor about any symptom that lasts or worries you, such as a new lump, unexplained weight loss, or a sore that will not heal, and keep up with recommended screenings. Early detection greatly improves outcomes.