An introduction to cancer in general
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Cancer known medically as a malignant neoplasm, is a term for a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably which involved mitosis, forming malignant tumors, and invade nearby parts of the body. Cancer is one of the major health diseases in Malaysia. According to The Cancer Incidence in Peninsular Malaysia 2003-2005 report that have been released on early 2008, breast cancer is the biggest threat in almost 70 000 new cases that were reported over two year period lately. The new cases were diagnosed among Malaysian in Peninsular Malaysia. The total 67,792 new cases were diagnosed among 29,596 males (43.7 per cent) and 38,196 females (56.3 per cent). The annual crude rate for males was 100.2 per cent per 100,000 population, and 132.1 per cent per 100,000 for females.
Healthy cells control their own growth and will destroy themselves if they become unhealthy. Cell division is a complex process that is normally tightly regulated. Cancer occurs when problems in the genes of a cell prevent these controls from functioning properly. These problems may come from damage to the gene or may be inherited, and can be caused by various sources inside or outside of the cell. When the genes are abnormal they are called oncogenes. About 100 of these have been discovered. A single faulty cell may divide to form a clone of identical cells. Eventually an irregular mass of relatively undifferentiated cells called a tumour is formed. Tumour cells can break away and spread to other parts of the body, particularly in the bloodstream or lymphatic system, causing secondary tumours ot metastases. This process is called matastasis. Tumours that spread and eventually cause ill health and death are described as malignant. The majority of tumours, such as common warts, do not spread and are describe as benign.[1]
Structure | |
Normal Cells | Cancer Cells |
DNA in genes and chromosomes go about their business in a normal way. | Cancer cells develop a different DNA or gene structure or acquire abnormal numbers of chromosomes. |
Cells divide in an orderly way to produce more cells only when the body needs them. | Cells continue to be created without control or order. If not needed, a mass of tissue is formed which is called a tumor. |
Energy | |
Normal Cells | Cancer Cells |
Cells derive 70% of their energy from a system called the “Krebs Cycle.” | Cells have a defective “Krebs Cycle” and derive little or no energy from it. |
Cells derive only 20% of their energy from a system called “Glycolosis.” | Cancer cells derive almost all their energy from “Glycolosis.” |
Cells derive most of their energy with the use of oxygen. | Cells derive most of their energy in the absence of oxygen. |
Blood Vessels | |
Normal Cells | Cancer Cells |
Cells have a built-in blood vessel system. | Cells do not have a built-in blood vessel system. They require more of certain amino acids to grow. |
Growth Factors | |
Normal Cells | Cancer Cells |
While similar to cancer cells, the amount of them is more in balance to produce a more normal level of activity. | These cells have over produced, require more chemicals (food) and are over active. |
Functions | |
Normal Cells | Cancer Cells |
The enzymes and hormones go about business in a normal balanced manner. | The enzymes and hormones are either over active or under active. |
Tumors are Different | |
Benign | Malignant |
Benign tumors are not cancerous. They do not invade nearby tissues nor spread to other parts of the body. They can be removed and are not a threat to life. | Malignant tumors are cancerous. They can invade and damage nearby tissues and organs and they can break away and enter the blood stream to form new tumors in other parts of the body. The spread of cancer is called metastasis. |
Determining what causes cancer is complex, and it is often impossible to assign a specific cause for a specific cancer. Changes in genes are mutations and any factor bringing about mutation is called a carcinogen. Most mutated cells are either destroyed by the body’s immune system or die with no-ill effect on the body. Many things are known to increase the risk of cancer, including retroviruses, DNA viruses, hereditary preposition, ionizing radiation, ultraviolent light, radon gas and chemical mutagens. These can directly damage genes or combine with existing genetic faults within cells to cause the disease. A small percentage of cancers, approximately five to ten percent, are entirely hereditary.[2]
| Factors that increase the risk of cancer | Explanation |
| Ratroviruses | Retroviruses are RNA viruses which, when they invade animal cells, use the enzyme reverse transcriptase to make DNA copies of the viral RNA. The DNA is inserted into the host DNA where it may stay and be replicated for generations of cells. Some retroviruses are harmless. Example of harmful retrovirus are HIV. |
| DNA viruses | DNA viruses contain DNA as their hereditary material. Some contain their own oncogenes which can cause uncontrolled cell division of host cells. Examples which infect humans are the papilloma viruses which caused warts. |
| Hereditary preposition. | Some cancers tend to run in families. More than 40% of cancer falls in this category which includes breast cancer. The genes responsible may be oncogenes, or genes which lead failure to kill cancer cells. For example, Retinoblastoma which starts in the eye and spreads to the brain, causing death if untreated. |
| Ionising radiation | This includes X-rays and particles from the decay of radioactive elements. The radiation causes the formation of chemically active and damaging ions inside cells which can break DNA strands or cause mutations. The types of cancer linked with ionizing radiation include skin cancer, bone marrow cancer and breast cancer. |
| Ultraviolent light. | This is the most common form of carcinogen radiation and is noon-ionising. DNA absorbs ultraviolent light and the energy is used in converting bases into more reactive forms which react with surrounding molecules. Sunlight contains ultraviolent light and prolonged exposure to it can result in skin cancers. |
| Radon gas | Radon gas is a natural source of radiation released from certain rocks such as granite. It may accumulate in houses in areas where these rocks are found. It has been linked to the development of leukaemia. |
| Chemical mutagens | For example, tobacco smoke contains chemicals responsible for lung cancer. The most important of these are polycyclic hydrocarbons which are converted in the body to carcinogens. |
Cancer can be detected in a number of ways, including the presence of certain signs and symptoms, screening tests, or medical imaging. Once a possible cancer is detected it is diagnosed by microscopic examination of a tissue sample. Cancer is usually treated with chemotherapy, radiation therapy and surgery. The chances of surviving the disease vary greatly by the type and location of the cancer and the extent of disease at the start of treatment. While cancer can affect people of all ages, and a few types of cancer are more common in children, the risk of developing cancer generally increases with age. In 2007, cancer caused about 13% of all human deaths worldwide (7.9 million). Rates are rising as more people live to an old age and as mass lifestyle changes occur in the developing world.
