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What Is Cancer?

The term “cancer” refers to a group of over 100 diseases in which cells grow and spread without control. In a normal cell, growth is controlled so that the rates of new cell growth and old cell death are kept in balance. In some cells, this balance is no longer present because new cells grow too fast and old damaged cells do not die off as they should. Over time, these cells form a growth called a tumor.

Tumors are classified as “benign” or “malignant” based on whether they spread. Because benign tumors do not spread to other parts of the body, they are not considered cancerous. Malignant tumors are considered cancerous because they have the potential to spread to other parts of the body. A malignant tumor, or “cancer,” is generally a more serious health problem than a benign tumor.

Cancers spread through the body in two ways: invasion or “metastasis.” Invasion occurs when cancerous cells spread to other tissues in the same area. Metastasis occurs when cancerous cells enter the lymph system and bloodstream and travel to other parts of the body. Metastasized cells then begin growing at the new site(s).

Tumor development is usually a slow process. Some cancers may be developing for up to 30 years before they can be detected. This makes it difficult to study the causes of cancer. People diagnosed with cancer today in Delaware may have been living in another state or country when their cancer began. In addition, the environment is constantly changing. Conditions in Delaware 30 years ago that may have contributed to cancer may no longer be present in today’s environment.

Who Gets Cancer?

Cancer is the second leading cause of death in the United States, exceeded only by heart disease. A new cancer is found every 30 seconds in the United States.  Men have a one in two chance of getting cancer while women have a one in three chance of getting cancer.

Prostate cancer is the most commonly diagnosed cancer in men. Breast cancer is the most commonly diagnosed cancer in women. For both men and women, lung cancer is the second most commonly diagnosed cancer and colorectal cancer is the third most commonly diagnosed cancer.

In general, the odds of developing cancer increase as you age. About three out of four new cancers are diagnosed in people aged 55 or older. There are, however, some cancers that predominantly affect children. These cancers are known as pediatric cancers.

In general, people diagnosed with cancer now live longer than they did in the past. This is due, in part, to cancers being found earlier. This is also due to improved methods for treating cancers once they are found.

What Causes Cancer?

We do not know everything that causes cancer. Research shows that cancers usually develop due to complex interactions between heredity, lifestyle, and environmental factors. These are known as risk factors. The risk of developing cancer increases as more risk factors are present.

Additionally, different types of cancers have different risk factors. For example, heavy alcohol use is a risk factor for liver cancer but is not a risk factor for skin cancer.

Internal Factors

Some factors that cause cancer are related to systems inside the body. For example, abnormal hormone levels in the bloodstream can cause cancer. A weakened immune system can also lead to cancer. Hereditary factors can also increase the risk of developing cancer. For example, research shows that inheriting a particular type of gene predisposes some women to developing breast cancer. Additionally, already having one genetic syndrome may make it more likely that a person will develop cancer. For example, research shows that children with Down syndrome may be at greater risk for developing certain types of cancer.

External Factors

Other factors that cause cancer are affected by factors outside your body. These external factors can be divided into lifestyle and environment categories. We can control our exposure to many of these factors. Exposure to environmental factors can be harder to control than lifestyle factors.


  • Tobacco Use—Tobacco use and regular exposure to tobacco smoke are known to cause lung, bronchus, kidney, and oral cancers. Smoking causes between 85% and 90% of all lung cancer.
  • Diet—A high-fat diet increases the risk of developing colorectal, uterine, and prostate cancers. Being overweight or obese is also linked to several types of cancer. On the other hand, eating a healthy diet may help protect you against some types of cancer.
  • Alcohol Abuse—Chronic, heavy alcohol use increases the risk of developing breast, oral, liver, and esophageal cancers. Research suggests that the cancer risks from alcohol use may be more pronounced for smokers.


  • Sunlight—Ultraviolet radiation from the sun, sun lamps, and tanning beds damages the skin and can cause skin cancer.
  • Chemical Exposure—Exposure to metals, chemicals, or pesticides in your workplace or home environment can increase the risk of cancer. Asbestos, nickel, cadmium, uranium, radon, vinyl chloride, benzidine, and benzene are well-known examples of carcinogens (substances which can cause cancer) in the workplace.
  • Radiation—Excess exposure to certain kinds of radiation may increase the risk of cancer. For example, exposure to radon gas may increase the risk of lung cancer, especially among smokers. To reduce chances of cancer, medical and dental X-rays are adjusted to deliver the lowest dose of radiation possible.
  • Viruses—Some cancers, such as cervical cancer, may be caused by viruses. Even though viruses are contagious (spread from person to person), cancer is not contagious. Additionally, not everyone exposed to the virus will develop cancer.

Exposure to a harmful agent does not automatically mean that a person will develop cancer. For example, two people may have the same exposures, but only one will get cancer. Whether or not a person who is exposed to a harmful outside agent develops cancer depends on many things. It matters how often and for how long the person is exposed. It also matters if the person is exposed to other agents as well. A person’s age, genetic make-up, and lifestyle behaviors collectively affect one’s risk of developing cancer.