The four major types of cancer


By Saul Gwakuba Ndlovu

ZIMBABWE’s former Government of National Unity’s Prime Minister and the MDC-T leader, Morgan Tsvangirai, recently succumbed to cancer of the colon, a disease against which he bravely struggled and ended up in the hands of some of South Africa’s cancer specialists.
It is important to note that there are many kinds of cancers, and also that cancer develops in any body tissue.
Medical experts say there are generally several patterns of abnormal development in every otherwise normal body tissue.
They add that there are many classes and sub-classes of cancer, but that there are four major kinds, which are carcinomas, sarcomas, lymphomas and leukemias.
Carcinomas comprise the largest cancer group and usually originate in the epithelial cells, that is, in the tissues that form the layer of the body and line up many of its hollow structures and tubes.
Those cells cover the body’s cavities and enable glands to function.
Sarcomas are the cancer that attack the body’s supporting parts such as bones, muscles, blood vessels and any fibrous tissues.
Lymphomas develop and attack the body’s glands that supply it with a colourless fluid that contains white blood cells.
The fluid is drained from various tissues and is conveyed by the body’s lymphatic system.
The leukemias are the cancers that develop in the tissues which produce blood cells such as the lymph nodes and the bone marrow.
Causes of cancer include human habits such as the consumption of tobacco and alcohol.
A 100 or so years ago, it was strongly thought that cancer was a hereditary disease.
That did not explain how the very first cancer patient got the disease for him or her to pass it on to posterity.
However, now medical science understands what occurs to body cells for them to become cancerous.
Scientists say there is a fault in the body’s control mechanism for cancer to occur in or on the human.
Exactly what would have happened for the cells to have a fault in their normal control mechanism is not known.
It is still a complicated medical puzzle wrapped in a physiological enigma inside nature’s world of mysteries, as Winston Churchill would have probably stated it.
What are known to medical scientists about cancer are what they refer to as ‘pre-disposing factors’.
Those are also divided into four categories: Physical agents, biological agents, life and health circumstances and finally, chemical agents.
The main physical agent that may cause cancer is exposure to excessive sunlight, the major cause of skin cancer to farmers, sailors and other people whose work exposes them to the sun’s ultraviolet rays.
Of much interest to the dark-skinned people, including black Zimbabweans, is that the incidence of cancer is far lower among them because the pigment in their skin screens their epidermis from those dangerous sun’s rays.
It would be most helpful to those who use skin-lightening chemicals to know that their habit may lead to what dermatologists call ‘keratoses’, an intermediate stage between a normal skin and a skin attacked by cancer.
After keratoses may follow cancer.
People working with X-ray machines for long periods without suitable protective clothing may develop cancer because of radiation.
Research conducted as early as 1940 discovered that among medical workers exposed to X-rays, leukemia occurred 10 times more than among those who are not.
People exposed to the dust of a certain type of asbestos for long periods have also developed cancer, but of the lungs.
This is a controversial medical issue because of its adverse effect on the mining and use of asbestos in general, and is presently being widely discussed and disputed by relevant industrial circles throughout the world.
Tobacco smoking, particularly pipe smoking, has been found to be an aggravating factor in the occurrence of cancer of the tongue, lips and the lining of the mouth.
The mouth is one of the human body’s nine apertures in the case of male people as females have an additional aperture in the form of the vagina.
The other apertures are the anus, the urinary duct, the nostrils, the eyes and the earholes.
We are not here including the body’s millions of pores which are also, in fact, apertures.
Dermatologists say scars cause by continuous irritation are much more likely to be attacked by cancer than normal skins.
Recently, medical studies have found that cancer has a higher incidence among people who take immunosuppressive drugs than among patients who do not. Such drugs are, however, vital to people who have had some transplants.
Medical doctors say that since the body’s immune system helps in disease resistance, when the system or mechanism is depressed, the body is less able to keep away cancer.
Cigarette smoking certainly increases the incidence of cancer, and to make this most unfortunate, in all tissues that come into frequent contact with the cigarette smoke.
It is believed the tar in that smoke causes the cancer, especially lung cancer.
Other body parts that also get affected are the trachea, the pharynx, the bronchi, the larynx and all other air sacs through which cigarette smoke and other gases circulate.
Alcohol has also been identified as one of the chemical agents that predispose one to cancer; it being understood that the difference between physical and chemical agents is very minor.
A combination of tobacco smoke and alcohol increases the cancer incidence.
Some medical scientists are of the opinion that cancer may be caused by some type of virus and hope that a cancer antiviral vaccine will be developed one day.
Meanwhile, there is no scientific evidence that any type of human cancer is caused by a virus.
As research progresses, it can be hoped that a cancer cure will be found with the passage of time.
Life and health circumstances play a part in the incidence of cancer, and so does age as doctors say certain cancers occur much more in childhood and others in old age.
Worldwide, cancer has been the major cause of death among children aged between one and 14 years.
It has also been discovered that cancer deaths occur mostly among the one-to-five year old children.
Research has found out that cancer of the breast is more common among unmarried than among married women.
It has also been discovered that women who have their first children before they are 25 years old have less risk of breast cancer than those who have their first children after the age of 35 years.
The incidence of cancer in the uterine cervix has been found to be higher among women who get married in their teens, or who have their first sexual intercourse while they are in their teens than those who get married in their 20s or those who never get married at all.
All these are important statistics, but the most important thing to do about cancer is to get it treated by properly qualified medical doctors in its very earliest stage.
That simply means getting medically examined regularly at the clinics, hospitals or by one’s doctor.
Early treatment may add more years to one’s life, and so would avoiding the consumption of that which is known to cause cancer.
The author of this article decided to study the causes and nature of cancer while in Swaziland in the early 1990s while he himself was briefly suffering from prostate cancer.
It was immediately successfully treated by Dr Jolly Mkwananzi back home in Bulawayo.
Saul Gwakuba Ndlovu is a retired, Bulawayo-based journalist. He can be contacted on cell 0734 328 136 or through email:


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