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What is cancer Cancer is a disease caused by normal cells changing so that they grow in an uncontrolled way. The uncontrolled growth causes a lump called a tumour to form. If not treated, the tumour can cause problems by spreading into normal tissues nearby or by causing pressure on other body structures. This is all explained more fully below. There are over 200 different types of cancer because there are over 200 different types of body cells. For example, cells that make up the lungs can cause a lung cancer. There are different cells in the lungs, so these may cause different types of lung cancer Cancer may begin as a single, genetically abnormal cell. As this one cell divides, it eventually becomes a tumor and develops a blood supply to nourish its continued growth. At some point, cells may break off from the primary mass and move to other parts of the body and could cause other types of cancer. Normal Cells QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Genes and Cancer Different types of cells in the body do different jobs, but they are basically similar. They all have a centre called a nucleus. Inside the nucleus are the genes. Genes are really bits of code. The information they carry can be switched on or off. The genes control the cell. They decide when it will reproduce, what it does and even when it will die. normal cell Normally the genes make sure that cells grow and reproduce in an orderly and controlled way. If the system goes wrong for any reason, the usual result is that the cell dies. Rarely, the system goes wrong in a way that allows a cell to keep on dividing until a lump called a 'tumour' is formed. Your body is made up of billions of cells that can only be seen under a microscope. These cells are grouped together to make up the tissues and organs of our bodies. They are a bit like building blocks. Different types of body tissues are made up of different types of body cells. For example, there are bone cells in bone and breast cells in the breast. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Cancer Cell Division When it comes to cell division, cancer cells break just about all the rules! The amount of time it takes for cell division to completely take place ranges widely, depending on the species involved: some bacteria, for example, can complete cell division in 20 minutes, while mammals such as humans may take 12-24 hours. In the case of growing organisms like a fetus or a young animal, cell division takes place rapidly because the organism cannot grow and thrive without a rapid replication of cells, especially in the case of an embryo. Fully grown organisms divide cells on a much slower scale, to slowly renew the body, except in areas like the skin and bone marrow, which are constantly generating new cells. If an injury is sustained, the cells can divide more quickly to heal the area. However, cell division can get out of control. This rapid growth of cells is known as cancer, and produces characteristic clusters of cells that take the form of tumors and other growths, which can kill if left untreated. The reason for out of control cell division is unknown, although scientists have shown that some substances can stimulate rapid cell division. These substances, or carcinogens, are required by law in many places to be labeled as a health risk. The mutated cells which double into cancers must also be completely eliminated from the body for the risk to be reduced to zero, as the cells may continue to reproduce if left alone. For this reason, many cancer treatments are very radical, to ensure that all of the harmful cells are excised from the body to prevent a recurrence. Cancer cells can divide without appropriate external signals. This is like a car moving without having pressure applied to the gas pedal. An example would be the growth of a breast cancer cell without the need for estrogen. Usually, the breast cells will only multiply when estrogen, a chemical sent from a gland in the brain, is present. However, in breast cancer cells, the cells bypass the need from estrogen to begin their division, resulting in uncontrolled growth. Cancer cells do not exhibit contact inhibition. While most cells can tell if they are being 'crowded' by nearby cells, cancer cells no longer respond to this stop signal. The continued growth leads to the piling up of the cells and the formation of a tumor mass. Cancer cells can divide without receiving the 'all clear' signal. While normal cells will stop division in the presence of genetic (DNA) damage, cancer cells will continue to divide. The results of this are 'daughter' cells that contain abnormal DNA or even abnormal numbers of chromosomes. These mutant cells are even more abnormal than the 'parent' cell. In this manner, cancer cells can evolve to become progressively more abnormal. In other words, these cells are passing are passing on their “abnormal” traits to new cells in your body. As a result, more and more cells in your body grow uncontrollably.