How Cancer Develops
When the normal control mechanisms that regulate the growth of cell fail, a neoplasm (‘new formation’) or tumor occurs. If this altered growth is totally out of control and causes the cells to invade other tissues, it is described as malignant. Malignant tumors from connective tissue cells are called sarcomas and those from the blood cells are called leukemia or lymphomas.
Spread of malignancy may be by direct invasion of neighboring tissues, or by cancer cells entering the bloodstream and becoming established in a distant organ or tissue, or when cancer cells are spread by the lymphatic system to involve nearby glands (lymph nodes). Occasionally spread occurs along natural body passages or cavities. For example, cancer cells from the stomach may travel to a pouch within the abdomen between the rectum and vagina. Symptoms resulting from cancer may be due either to a direct effect of the invasion of surrounding tissues or to the more distant spread.
A site at which a cancer first develops is called primary site. The sites to which cancer may seed are called secondary sites.
How cancer develops
The exact mechanism by which normal cells become malignant is not fully understood. It is assumed that there is a spontaneous failure of a obvious percentage of cells to remain ‘normal’. The percentage increases when there is an hereditary tendency to certain types of cancer within families, and also when the amount of irritation or pain done to a cell is excessive.
The relationship between long-term exposure to sunlight and the development of skin cancers; between exposure to nuclear radiation and leukemia development, and between smoking and lung cancer are well known examples of this type of cell irritation. Viruses are thought to play a role in the development of some tumors.
It appears that the immune system of the body normally counteracts malignant cells. In situations where the immune system becomes ineffective, due to old age, severe illness, or the expend of special immunosuppressive drugs in kidney transplants, tumors are much more frequent.
Disease distribution
The relative occurrence of different types of cancer varies according to sex, age and geographical distribution. Cancer appears to be more common in today’s population, but this is partly because people are living longer and because other problems of infection and nutritional disturbance are now more adequately controlled.
The most approved cancers in adult males are those of the skin, lung, astronomical bowel, stomach and prostate, and leukemia and lymphoma; in adult females those of the breast, uterus, large bowel, skin and stomach, and lymphomas and leukemia. Children are less prone than adults to develop cancer; leukemia, lymphomas and kidney and brain tumor are most common malignancies in this age group.
Symptoms
Various symptoms may be early indications of a developing cancer, and although in most cases the particular symptoms will explain to be the result of some other condition, medical assessment is needed to rule out the possibilities of cancer. Eight warning signs of a developing cancer are:
1. A new lump or swelling that persists for more than 4-6 weeks, especially in the breast.
2. Abnormal bleeding, particularly from the bowel, breast or vagina.
3. Indigestion or other abdominal symptoms that persist for more than 4-6 weeks.
4. Constipation or diarrhea (or alternation of the two) that has been note for more than 4-6 weeks.
5. Hoarseness of the voice or difficulty in swallowing present for more than 4-6 weeks.
6. Any sore in the skin or lining of the mouth that has not healed within 4-6 weeks.
7. Any change in the size and shape of the mole or wart; persistent bleeding or itching should also be checked.
8. Sudden or unexplained loss of weight.
Early diagnosis is the key to successful treatment of cancer. The often quoted statement ‘cancer is a diagnosis, not a sentence’ is certainly suitable, and it be remembered that cancers can be detected before they cause symptoms, either by the patient (as with cancer of the breast) or by the examining doctor (as with cancer of the cervix).
Source:
How Cancer Develops, eCancerAnswers
Types and Symptoms of Cancer, eCancerAnswers
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