Cancer Diseases

What is cancer ?

Cancer is one of several disorders which can result when the process of cell division in a person's body gets out of control. Such disorders produce tissue growths called 'tumors'. A cancer is a cer-tain kind of tumor.

Cancer attacks one in every four people.

Normal Cell Division

The body is constantly production new cells for the purpose of growth and repair- about 500,000 million daily. It does this by cell division - one parent cell divides to form two new cells. When this process is going cor-rectly, the new cells show the same characteristics as the tissue in which they originate. They are capable of carry-ing out the functions that the body requires that tissue to perform. They do not migrate to parts of the body where they do not belong; and if they were placed in such a part artificially they might not survive.

Tumors

in a tumor, (he process of cell division has gone wrong. Cells multiply in an uncoordinated way. indpendent of the normal control mechanisms. They produce a new growth in the body, that does not fulfill a useful function. This is a tumor, or "neoplasm". A tumor is often felt as a hard lump, because its cells are more closely packed than normal. Tumors may be "benign" or "malignant". A cancer is a malignant tumor. That is, it may continue growing until it threatens the continued existence of the body.

Benign Tumors

in a benign tumor, the cells reproduce in a way that is still fairly orderly; they are only slightly different from the cells of the surrounding tissue; their growth is slow and may stop spontaneously; the tumor is surrounded by a capsule of fibrous tissue, and does not invade the normal tissue; and its cells do not spread through the body.

A wart is a benign tumor. Benign tumors are not fatal unless the space they take up exerts pressure on nearby organs which proves fatal. This usually only happens with some benign tumors in the skull.

Malignant Tumors

In malignant tumors, the cells reproduce in a com-pletely disorderly fashion.

The cells differ considerably from those of the sur-rounding tissue. (Generally, they show less specializa-tion.)

The tumor's growth is rapid, compared with the sur-rounding tissue.

The tumor has no surrounding capsule, and can there-fore invade and destroy adjacent tissue.

The original tumor is able to spread to other parts of the body by metastasis and produce secondary growths there.

A malignant tumor is usually fatal if untreated, because of its destructive action on normal issue.

Biopsy

A biopsy is the most certain way of distinguishing between benign and malignant tumors. A piece of the tumor is surgically removed, and then studied under a microscope.

Cancer Growth

Cell Division

Cancerous cells cannot divide faster than normal cells. But normal cell division reaches its maximum rate only in times of injury and repair. Cancerous growths are contin-ually producing cells at this maximum rate without check. They are less successful than normal tissue could be, because many of the faulty cancerous cells die. Nevertheless, the result is that cancerous growths grow faster than normal tissue.

Metastasis

Metastasis is the process by which cancerous cells trav-el from the original (primary cancer site to other parts of the body.

It occurs when cancerous cells get caught up in the flow of blood or lymph. the cells are carried along in the vessels, until they lodge in another part of the body. If they succeed in establishing themselves there, this becomes a new (secondary) cancer site. If a secondary site gets large enough, it can also metastasize in turn.

Cancer that has metastasized along the lymph vessels normally sets up its secondary sites in the gland. Cancer that has metastasized in the blood stream sets up sec-ondary sites in the hones, lungs, and liver. Cancers in (he brain do not metastasize but cancers elsewhere can metastasize to the brain. Some sites are more receptive than others.

Common locations for secondary growths include the lungs, bones, brain, kidney and bladder, and larynx, the testes in men and the breasts in women. A cancer can also spread through the body simply by the process of growth.

Causes of Cancer

Chromosome Damage

The characteristics of a cell are inherited from its par-ent cell. They are passed on in the DNA in the chromo-somes. This forms a set of coded instructions, which con-trols the cell's structure and function. In cancerous cells, the characteristics of malignant growth are passed on from one generation to another. This means that the genetic code must have been damaged.

This in fact, is seen if the chromosomes of cancerous cells are examined. Normal cells have 46 chromosomes arranged in 23 pail's. Almost all cancer cells are abnormal in the number and/or structure of these chromosomes.

Normal Deviancy

Cells with genetic defects appear in the body every day: so many millions of cells are being made. that some mistakes are inevitable. But most die almost immediately, because they are too faulty to survive, or because they are recognized as abnormal and eaten by white blood corpuscles.

Others are only slightly defective; and not malignant. Only very rarely do malignant cells survive and reproduce successfully. Appearance of cancer in a person may sim-ply be due to this unlucky change. Alternatively, it may be that the body has "immunity" to such malignant cells, and that this sometimes breaks down. This would explain why cancer can remain "dormant" in a person for many years.

Special Factors

A few factors have been recognized that do make genet-ic damage in cells more likely. But they can only explain a tiny proportion of the cancer that occurs.

a. Certain chemicals can cause cancer to form. if they are repeatedly in contact with the body over a period of time. Such chemicals are called carcinogens, and include some hydrocarbons. Apart from tobacco smoke, these carcinogens usually only affect workers whose job brings them into regular contact with them. (However, atmospheric pollution may also be slightly carcinogenic.)

b. Certain viruses can pass malignant tumors from one animal to another, and the same may occur in man. But so far only one rare form of cancer is thought to be caused this way. Apart from this. human cancer seems not to be virus induced and therefore not infectious.

c. Ionizing radiation. Without correct protection, X rays can cause skin cancer, and radiation can cause leukemia. Also ultraviolet rays (as in sunlight) may cause skin cancer in some circumstances.

d. Continued physical irritation. There is disagreement over (his. but some experts believe that continued physical disturbance of the skin or mucous membrane can cause cancer.

If so the sharp edges of a broken tooth, for example, could eventually cause a cancer in the mouth.

Others argue that such irritation can only accelerate an existing cancerous growth.

Correlative Factors

Some individuals are more likely to develop cancer than others.

a. Heredity : Actual cancerous growths are not inherited. But a pre-disposition for cancer can be passed on. It may be that some inherited characteristics make a person's cells more likely to become malignant.

b. Age : Most cancers occur in the 50 to 60 age group. However. children and adolescents are susceptible to leukemia, brain tumors, and sarcomas of the bone.

c. Sex : In almost all countries, cancer occurs more frequently in men than in women.

d. Geographical location : Eg, for some unknown reason, gastric cancer is most frequent in coastal countries with cold climates.

e. Cultural habits : Eg, cancer of the penis is less; common in societies where circumcision is usual.n

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