Cancer: Introduction

Cancer is a group of diseases characterised by uncontrolled cell division which leads to growth of abnormal tissue. This means that a cancer is essentially a disease of mitosis. Cancer begins when a single cell is transformed, or converted from a normal cell to a cancer cell. Cancer cells grow and divide uncontrollably to form a mass of cancer cells called a tumour. As the tumours grow, they squash healthy cells, steal their nutrients and prevent them from working normally. Cancer cells differ from normal cells in a number of ways:

  1. Cancer cells don’t listen to signals to stop growing: normal cells listen to signals from the body to stop growing and dividing. However cancer cells do not respond to signals from the body and keep on dividing.
  2. Cancer cells grow new blood vessels: as the tumour grows larger, it begins to release proteins from the cell to attract new blood vessels. Blood vessels draw nutrients away from healthy cells and therefore starve them while allowing the growth of the tumour. The new blood vessels also enable cancer cells to enter the bloodstream and spread to other parts of the body.
  3. Cancer cells spread around the body: another feature of cancer cells is that they can spread around the body (metastasise). Tumours that have the ability to spread to other parts of the body are called malignant. Cancer cells can spread to surrounding tissues via the bloodstream or via the lymph system.

As previously mentioned, cancer cells are malignant which means they are able to invade tissues and spread to other parts of the body. Some tumours cannot spread to other tissues and are called benign tumours. Benign tumours are non-cancerous.


Types of Cancers

Cancer can affect almost any tissue in the body. A list of some common cancers includes:

  • Breast cancer
  • Lung cancer
  • Oesophageal cancer
  • Leukaemia (blood cancer)
  • Melanoma (skin cancer)


There are hundreds of different types of cancer. The most common types are breast cancer, prostate cancer, basal cell cancer, melanoma, colon cancer, lung cancer, leukemia and lymphoma. For a comprehensive list visit

Cancers often spread to different organs, however it remains the same type of cancer as the original cancer, it is simply referred to as a metastasis. Therefore melanoma (skin cancer) that spreads to the liver is not liver cancer, but a melanoma metastasis to the liver.

Video: How Healthy Cells Become Cancerous

In the short video below, find out how and why a normal cell becomes a cancer cell, risk factors and treatment.

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This is a lesson from the tutorial, Introducing the Cell and you are encouraged to log in or register, so that you can track your progress.

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