الوسم: الانجليزي

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Even though cancer is not common in children, it is the most common cause of death from illness in children between the ages of 1 and 15. This is because children today are at much lower risk of dying from infectious diseases than they were 80 years ago. So although the percentages of children dying from various cancers have gone down, the proportion of childhood deaths from cancer overall has gone up.

Types of childhood cancer

The most common types of childhood cancer are

• Leukaemias, diagnosed in 1 in 3 children with cancer
• Cancers of the brain and spinal cord, diagnosed in 1 in 4 children with cancer

The other rarer types of children’s cancers include retinoblastoma (a type of eye cancer), Wilm’s tumours (a type of kidney cancer), muscle or bone cancers (osteosarcoma, rhabdomyosarcoma, Ewings sarcoma) or lymphoma (cancer that starts in the lymphatic system).
We have a general section about acute lymphoblastic leukaemia (the most common type of childhood leukaemia) and another about brain tumours. These sections are about adult cancer, rather than children’s cancers. But much of the information about causes, diagnosis and treatment will be the same

What causes cancer?

There is no one single cause for cancer. Scientists believe that it is the interaction of many factors together that produces cancer. The factors involved may be genetic, environmental or constitutional characteristics of the individual.

Diagnosis, treatment and prognosis for childhood cancers are different than for adult cancers. The main differences are the survival rate and the cause of the cancer. The survival rate for childhood cancer is about 72 percent, while in adult cancers, the survival rate is 60 percent. This difference is thought to be because childhood cancer is more responsive to therapy, a child can tolerate more aggressive therapy and the prognosis is better.

Childhood cancers often occur or begin in the stem cells, which are simple cells capable of producing other types of specialized cells that the body needs. A sporadic (occurs by chance) cell change or mutation is usually what causes childhood cancer. In adults, the type of cell that becomes cancerous is usually an "epithelial" cell, which are cells that line the body cavity and cover the body surface. Cancer occurs from environmental exposures to these cells over time. Adult cancers are sometimes referred to as "acquired" for this reason.

from environmental exposures (usually over many years). There are three main types of genes that can affect cell growth and are altered (mutated) in certain types of cancers, including the following:
Oncogenes – these genes regulate the normal growth of cells. Scientists commonly describe oncogenes as similar to a cancer "switch" that most people have in their bodies. What "flips the switch" to make these oncogenes suddenly become unable to control the normal growth of cells and allowing abnormal cancer cells to begin to grow, is unknown.
Tumor suppressor genes – these genes are able to recognize abnormal growth and reproduction of damaged cells, or cancer cells, and can interrupt their reproduction until the defect is corrected. If the tumor suppressor genes are mutated, however, and they do not function properly, tumor growth may occur. Mismatch-repair genes – these genes help recognize errors when DNA is copied to make a new cell. If the DNA does not "match" perfectly, these genes repair the mismatch and correct the error. If these genes are not working properly, however, errors in DNA can be transmitted to new cells, causing them to be damaged.

Usually the number of cells in any of our body tissues is tightly controlled so that new cells are made for normal growth and development, as well as to replace dying cells. Ultimately, cancer is a loss of this balance due to genetic alterations that "tip the balance" in favor of excessive cell growth.

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