Cancer is the name for a disease that can affect cells from all the organs and body's structures and is considered to be life threatening. Cancer determines cells to divide in an uncontrollable way. Generally the cells of the body divide only when needed, like when they grow old and other cells need to be produced in order to replace them or when they are in a small amount and the body needs more of them.

Because the cells are produced in an increased number, a mass of unknown tissue will form, known as a tumor (this tumor can be benign or malign).

The benign form of the tumor is considered not to be harmful. It can be easily removed and will not spread to other organs. The possibility for this tumor to reappear is much reduced.

The malign form of the tumor is also known as cancer and is considered to be a threat to life. It can affect organs that are situated near the tumor and it can also get into the bloodstream or lymphatic system and reach other organs creating new tumors in the whole body. This is known as metastasis. The secondary disease will be named after the primary disease, because the metastatic cancerous cells have the same structure with the basic tumor cells.

Taking colon cancer for an example, if the colon cancer cells spread toward the liver and affect it, the liver disease will be called metastatic colon cancer.

In the whole world, colon cancer is the third leading cause of cancer in males and the fourth in women. It is quite rare in Asia and Africa but you can find it frequently in the Western world. Those who have adopted western diets are at risk to develop colorectal cancer. Doctors believe that this type of cancer is developing from polyps situated in the large intestine (colon and rectum are a part of the large intestine). These polyps are considered to be benign but left untreated for years they can transform in malign tumors. The polyps can be removed easily during a colonoscopy performed by the doctor.

Colorectal cancer can affect nearby structures and can even get into the bloodstream or lymphatic system and spread towards liver and lungs where it will produce another tumor. If metastasis has occurred, the hope of treatment efficiency is considered to have reduced drastically.