What is cancer?

Three out of four people will know someone affected by cancer. Learning and understanding more about cancer can help clear up confusion and misconceptions.

Cancer is the umbrella term for a group of more than 100 different diseases. The body is made up of trillions of living cells. Normal cells are generally dominant, growing, reproducing and dying in an orderly way. Cancer begins when abnormal cells — which are always present — begin growing rapidly and invading other normal cells. DNA is in every cell and it directs all of a cell’s actions. When DNA in a normal cell is damaged, the cell either repairs the damage or dies. In cancer cells, damaged DNA is not repaired. The cell doesn’t die, but goes on to make new cells that reproduce the same damage. It is rare to know exactly what caused any one person’s cancer.

Cancer is always named based on the place where it started. So colon cancer that has spread to the liver is called metastatic colon cancer, not liver cancer. In this case, cancer cells taken from the liver would be the same as those in the colon, so they would be treated in the same way. Different types of cancer can behave very differently, so there are different forms of treatment for each variation.