Cancer is a disease that affects people of all nationalities and age groups.

Cancer cells do not respond to signals that usually regulate cell growth and division. These cellsB grow unchecked, producing more and more cancer cells. Just as signals regulate cell growth and division, signals control cell death. Cancers can result from cells that do not die when they should. To grow beyond a certain size, tumors need a system to bring in nutrients and take out wastes.

The cancer cells that make up a tumor attract blood vessels to grow into the tumor mass. The blood vessels then nourish the tumor just like any organ in the body. Cells have a lifespan. The age of a cell and its ability to divide is related to structures b telomeres b found at the ends of chromosomes. Most of the deaths from human cancers (90%) are due to cancer cells spreading and establishing colonies in other parts of the body. Cancer cells are often different in shape and size to normal cells, and they no longer respond to signals that control normal cellular functions.

A cell carries the entire set of genetic instructions b the genome b that makes an entire organism. The instructions are encoded in DNA as genes and packaged as chromosomes in the nucleus. DNA is not immutable and is subject to damage and mutations. Crucial changes in the genome affect the chance and rate of the development of a cancer cell.

Our body's immune response is constantly surveilling for these emerging pre-cancers or pre-tumor cells. Successful cancers have to avoid detection long enough to grow into a tumor.