What Is Cancer?

Like many people, you may think of cancer as one disease. The fact is, cancer is actually a group of more than 100 diseases that can start almost anywhere in the body. In 2018, it is estimated that there will be more than 1.7 million new cases of cancer in the US, and more than 609,640 will from die from cancer. While cancer may be one of the leading causes of death in the US and around the world, the number of cancer survivors in the US is increasing, showing that real progress is being made in treating cancer in many of its forms. Read on to learn more about cancer and its treatment. Then talk with your healthcare provider about any questions you have about prevention, testing, or treatment.

In 2016, there were estimations of more than 15 million cancer survivors in the US. That number is expected to grow to 20.3 million by 2026.

How does cancer develop?

To understand how cancer starts, it’s important to understand the role of cells. Cells are the structures that, together, make up our body. They grow and then divide to continually make new cells as our body needs them. When a cell is too old or not healthy, it usually dies. This is normal. New, healthy cells then take their place.

Cancer starts in the body when cells grow uncontrollably and crowd out normal cells. Sometimes, the cells mutate. Instead of dying, these abnormal cells grow and multiply too quickly and can form a tumor. Having a tumor does not mean you have cancer. Tumors can be either cancerous (malignant) or noncancerous (benign). Cancerous tumors grow and can spread to other parts of the body. Some types of cancers do this quickly and others do it more slowly. When cancer spreads to a different part of the body, it is still referred to by where it started. For example, if lung cancer spreads to the bones, it’s still considered lung cancer.

Noncancerous tumors grow but don’t spread. Certain cancers such as leukemia or lymphoma do not form tumors—they are cancers of the blood.

What causes cancer?

No one really knows why one person develops cancer and another does not. What researchers do know is that there are risk factors that can increase a person’s cancer risk. Some of these, such as lifestyle choices, can be controlled. Others, such as age, family history, and genetics, cannot be. Risk factors for cancer include:

Environmental factors such as air and water pollution, exposure to certain chemicals, and, for skin cancer, exposure to the sun.
Certain viruses and bacteria.
Lifestyle factors, such as alcohol and tobacco use, obesity, and food choices.
Family history.
Certain inflammatory health conditions, such as a long-lasting infection, and inflammatory bowel diseases, such as ulcerative colitis and Crohn’s disease.
Age—more than 50% of new cancers are diagnosed in people 65 and older.

What are the signs and symptoms of cancer?

Cancer can cause any number of signs and symptoms. These will also vary depending on where the cancer is, the size of the tumor, and if and where it has spread in the body. Some of the more general signs and symptoms of cancer include:

Weight loss that happens for no known reason.
Fever.
Feeling very tired.
Pain.
Headache that doesn’t go away.
Changes in the skin that can be seen or felt.

How is cancer detected?

Finding cancer early is key because early detection can increase the chance of being treated successfully. Because a person may not have any signs or symptoms of cancer, health organizations recommend cancer screenings. The American Cancer Society recommends that everyone over the age of 20 include cancer screenings as part of their regular medical exams.

How is cancer diagnosed?

There is no single test that can diagnose all of the different types of cancers. Healthcare providers can identify cancer in a number of ways, including:

Screenings such as colonoscopies, mammograms, and Pap smears.
Reviewing any signs and symptoms a person may have.
Finding lumps during a physical exam or through imaging tests.
As a result of tests for other health issues.

If cancer is suspected, further testing may be necessary to confirm the diagnosis. For most types of cancer, this usually means having a biopsy. During a biopsy, a healthcare provider removes a small piece of the suspicious tissue and examines it under a microscope.

What are cancer stages?

The stage of a cancer refers to the size of the tumor and if and how far it has spread in the body. Some types of cancer have their own staging system, but the TNM staging system is used most often by healthcare providers. In this system:

The T stands for the size and extent of the main tumor.
The N stands for the number of nearby lymph nodes that have cancer. Lymph nodes are small structures found throughout the body that help fight infection by attacking and killing germs.
The M stands for whether the cancer has metastasized, meaning that it has spread from the primary tumor to other parts of the body.

The TNM staging system describes cancer in detail. When healthcare providers describe the stages to patients, they may use the following less-detailed stages:

Stage 0: Abnormal cells have been found, but have not spread to tissue close by. This can be called carcinoma in situ (CIS), which is not a cancer, but can become a cancer.
Stage 1, Stage 2, and Stage 3: Cancer has been found. As the stage number increases, the larger the tumor may be and the more it has also spread to tissue nearby.
Stage 4: Cancer has spread to other areas of the body.

How is cancer treated?

There are a number of ways healthcare providers treat cancer, depending on the type of cancer you have and how advanced it is.

The most common cancer treatments include:

Surgery—A surgeon removes the cancerous tumors if possible.
Chemotherapy—Drugs are used to kill cancerous cells.
Radiation therapy—High doses of radiation are used to damage cancerous cells or decrease the size of tumors.

Other approaches include immunotherapy, which uses the body’s own immune system to fight the cancer, and targeted or personalized cancer therapy.

Personalized therapy is based on the finding that, in more than 90% of cancers, there is a change (mutation) to a person’s genes. By looking at the genetic make-up of each person with cancer, healthcare providers can sometimes offer patients customized treatment by seeing in advance:

If there are certain types of medicines that will work on the cancer, and
If the patient can tolerate the medicine.

If you or someone you know is diagnosed with cancer, remember that it’s important to play a role in the treatment process. Learn as much as possible about the diagnosis, ask questions, find the right healthcare team, discuss your treatment options, get support, and more.

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