Cancer – What Causes It?
Cancer is an abnormal growth of cells that spreads to other parts of the body and disrupts normal functions. It can lead to other diseases and kills many people worldwide every year.
It is the second leading cause of death among humans. It can affect all organs and tissues. It is caused by genetic mutations that are passed on from parents or develop in the womb. It can also happen if a person is exposed to chemicals or radiation.
Scientists don’t know what causes most cancers. Some are linked to lifestyle choices like smoking or sun exposure. Others are due to infections with viruses or bacteria. A small number of cancers are inherited from genes.
People may be diagnosed with cancer when they have symptoms or through screening tests. They are treated with surgery, radiotherapy, chemotherapy and other medicines. They may also have other treatments to ease symptoms and improve the quality of life.
It is a serious and sometimes fatal disease that can affect any part of the body, but it usually starts in cells in the skin, blood vessels, bones, muscle and other soft tissue. They grow very rapidly and form masses called tumours that can damage the surrounding healthy tissue and organs. They can even enter the bloodstream and travel to other parts of the body.
Cancer can be divided into different types according to the part of the body it affects. For example, some cancers grow in the bones or the lungs, while others affect the skin, brain, kidneys, liver or lymph glands. Cancers that start in the blood-forming tissue of the bone marrow are called leukemias. They do not form solid tumors, but instead, large numbers of abnormal white blood cells build up in the blood and bone marrow, crowding out the normal blood cells that carry oxygen to other tissues, control bleeding and fight infections.
The first step towards understanding cancer was to understand that living tissues are made of cells. The work of Hooke in the 1600s and Virchow in the 1800s showed that all cells are direct descendants of other cells. That explained how cancer cells can come from any normal cell and why they cannot be traced back to a single source.
In the early 1900s, scientists began to understand that some viruses can act as causative agents for cancer. However, it took much longer to recognise that most cancers are not caused by a single infectious agent but by the accumulation of many molecular changes over time. This step-by-step process is known as clonal evolution.
It explains several long-standing observations, such as the increase in cancer rates with age and the fact that most cancers are not found in young people. It also helps explain why it takes so long to diagnose most cancers, because the process of accumulating mutations that lead to the development of a cancerous tumor can take decades to complete. However, this does not mean that all cancers are preventable.
Cancer is an abnormal growth of cells that spreads to other parts of the body and disrupts normal functions. It can lead to other diseases and kills many people worldwide every year. It is the second leading cause of death among humans. It can affect all organs and tissues. It is caused by genetic mutations that are passed on from parents or develop in the womb. It can also happen if a person is exposed to chemicals or radiation. Scientists don’t know what causes most cancers. Some are linked to lifestyle choices like smoking or sun exposure. Others are due to infections with viruses or bacteria. A small number of cancers are inherited from genes. People may be diagnosed with cancer when they have symptoms or through screening tests. They are treated with surgery, radiotherapy, chemotherapy and other medicines. They may also have other treatments to ease symptoms and improve the quality of life. It is a serious and sometimes fatal disease that can affect any part of the body, but it usually starts in cells in the skin, blood vessels, bones, muscle and other soft tissue. They grow very rapidly and form masses called tumours that can damage the surrounding healthy tissue and organs. They can even enter the bloodstream and travel to other parts of the body. Cancer can be divided into different types according to the part of the body it affects. For example, some cancers grow in the bones or the lungs, while others affect the skin, brain, kidneys, liver or lymph glands. Cancers that start in the blood-forming tissue of the bone marrow are called leukemias. They do not form solid tumors, but instead, large numbers of abnormal white blood cells build up in the blood and bone marrow, crowding out the normal blood cells that carry oxygen to other tissues, control bleeding and fight infections. The first step towards understanding cancer was to understand that living tissues are made of cells. The work of Hooke in the 1600s and Virchow in the 1800s showed that all cells are direct descendants of other cells. That explained how cancer cells can come from any normal cell and why they cannot be traced back to a single source. In the early 1900s, scientists began to understand that some viruses can act as causative agents for cancer. However, it took much longer to recognise that most cancers are not caused by a single infectious agent but by the accumulation of many molecular changes over time. This step-by-step process is known as clonal evolution. It explains several long-standing observations, such as the increase in cancer rates with age and the fact that most cancers are not found in young people. It also helps explain why it takes so long to diagnose most cancers, because the process of accumulating mutations that lead to the development of a cancerous tumor can take decades to complete. However, this does not mean that all cancers are preventable.