What Is Cancer? [6,13]

Cancer is a disease that starts in our cells. Genes inside each cell order it to grow, work, reproduce, and die. Cancer cells develop because of damage or changes in these genes. The body is usually able to repair damaged genes. However, in cancer cells, the genes are not repaired.

Normally, cell growth, division, and death happen in an orderly fashion. But when the genes are changed or damaged, the orderly process may go wrong. These cells may form when the body does not need them. Also, old cells do not die when they should. In most cancers, this group of abnormal cells begins to form lumps or tumors. However, not all cancers form lumps. Leukemia, for instance, is a cancer that will not form a tumor, but rather affects the blood and organs that form the blood.

What Causes Cancer? [6,13]

Certain lifestyle and environmental factors can change some normal genes into genes that allow cancer cells to grow. This change may be the result of:

• Tobacco use
• Diet
• Exposure to ultraviolet (UV) radiation from the sun
• Exposure to carcinogens (cancer-causing substances) in the workplace or environment

People can also inherit damaged genes, which accounts for inherited cancers. A damaged inherited gene increases a person’s chance of developing cancer, but does not guarantee that cancer will develop.

Certain viruses, such as the human papillomavirus (HPV), hepatitis B and C, and human immunodeficiency virus (HIV), may also increase a person's risk of developing cancer.

What Is the Difference Between Benign and Malignant Tumors? [6,13]

Tumors can be either benign (noncancerous) or malignant (cancerous). Benign tumor cells stay in one place in the body and are not usually life-threatening.

Malignant tumors are cancer. Cells in malignant tumors divide without control or order, causing them to crowd out and replace normal tissue. The cancer cells may also break away from the malignant tumor and enter the bloodstream or lymphatic system. This can allow the cancer to spread from the original cancer site to form new tumors in other organs. This process is called metastasis. Even if cancer spreads to other organs, the name is determined by where it first began. For instance, if breast cancer spreads and forms a new tumor on the liver, it is still called metastatic breast cancer, not liver cancer.

What Is Staging? [5]

Staging is the process of finding out how far the cancer has spread. Staging is important in helping your doctor determine treatment options. It can also be used to help estimate your prognosis (likely outcome or course of disease).

While there is more than 1 system for staging, the TNM system is one of the most commonly used. This system has been accepted by the International Union Against Cancer (UICC) and the American Joint Committee on Cancer (AJCC). The TNM system is based on the extent of the tumor (T), the extent of spread to the lymph nodes (N), and the presence of metastasis (M). A number is added to each letter to indicate the size or extent of the tumor and the extent of spread. For example, a tumor classified as T1, N0, M0 is a tumor that is very small, has not spread to the lymph nodes, and has not spread to distant organs of the body.

Because each cancer type has its own classification system, the letters and numbers discussed above do not always mean the same thing for every kind of cancer. The T, N, and M are combined in order to assign an overall “stage” (I, II, III, or IV) to your cancer. Sometimes these stages are subdivided as well, using letters such as IIIA and IIIB.

In general, the lower the number, the less the cancer has spread. Stage I cancers are the least advanced and often have a better prognosis (likely outcome or course of disease). Higher-stage cancers are often more advanced, and treatment is more difficult.

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