|MadSci Network: Cell Biology|
Fiona, There are several basic reasons why tumors, and especially cancerous tumors, can cause problems. One is by crowding out healthy tissue. Another is by invading healthy tissue. A third is that as cancers grow, they act as parasites and take away what the body needs to survive. Let me explain each of these ideas in a little more detail, but first let me define some important terms. Tumors are abnormal growths in the body. They result when one type of tissue (skin, liver, lung, whatever) stops performing its regular function and begins to grow, usually usually at a faster pace than the rest of the tissue around it. Tumors may or may not be cancerous. Non-cancerous tumors are referred to as "benign". Cancers are also abnormal growths, but they differ from benign tumors by their ability to invade other tissue. For example, prostate cancer can spread to bone and breast cancer can spread to the lymph nodes. This spreading is called "metastasis". O.K., as I said, cancer can crowd out healthy tissue. A good example is brain cancer. If a tumor becomes large enough, it can put pressure on the brain and cause headaches, dizziness, changes in personality, etc. The healthy brain tissue may begin to die because of this pressure, so that this could be fatal. When cancer metastasizes, it can interfere with the function of the organ to which it spreads. This is because it kills normal tissue as it grows. If cancer spreads to lungs, for instance, it can inhibit a persons ability to breathe. Finally, cancer can take away valuable nutrients from the body. A person will begin to burn more calories when they have cancer because cancer is a growing thing. This is partly responsible for the weight loss people often experience with cancer. The cancer itself may also produce hormones that causes the victim to lose muscle and fat tissue. The extreme weight loss caused by the disease is called "cachexia". Cancer may also cause excessive bleeding, further weakening the person. To summarize, cancer has negative effects because it presses on and invades normal tissue and because it causes the body to use up its much needed resources. Oh yes, almost forgot...many of the treatments for cancer also cause problems including loss of appetite and a lack of energy. I hope that this helps. Gabriel
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