What Is Cancer?

Our body is made up of a vast collection of cells and every cell contains 23 pairs of chromosomes. Winding through each pair is a double spiral of DNA molecules, the genetic blueprint for life. Each of these molecules contains numerous numbers of genes.
Almost all our cells need to be replaced regularly. Some cells divide every few hours and are shed after living for only a few days. Others live for years. The process of all divisions and growth are controlled by genes that start and stop the growth process. Some of these growth-controlling genes may undergo changes (mutation) that cause them to malfunction and cell growth is then uncontrolled. Simple overgrowth may lead to harmless benign tumor (not likely to spread). However, some genes in a cell not only induce uncontrolled growth, but also cause the cell to invade and damage surrounding blood vessels, nerves, other body tissues or other parts of the body. The latter process is called metastasis.
Cancer starts with one abnormal cell. That cell divides and becomes two abnormal cells and then four abnormal cells and so on. Cells divide at various rates called doubling times. Fast growing cancer may double over one to four weeks, while slow growing cancer may double over two to six months. So there is a “silent” period after the cancer has started to grow. There is no lump or mass, and the tumor is too small to be detected by any means now known. After many months or years, the doubling process has occurred about 30 times or so. By then the lump may have reached the size of about 1cm that can be felt, seen on X-ray etc, although some new imaging techniques and laboratory tests may sometimes detect smaller tumors.