Cancer is an umbrella term for diseases that involve uncontrolled cell growth.

What causes cancer?

Cells in the body divide, mature and die in a regulated and orderly way. This process is controlled by specific genes inside the cells. Cancer happens when the genes mutate and lose control of this orderly process. When the genes lose control, cells grow and divide out of control, thus causing cancer.

What is a tumour?

Abnormal cells cluster together into lumps called tumours. If a tumour stays in one place in the body it is benign (non-cancerous). If the tumour starts to invade other tissues and spread to other parts of the body (through the blood stream or the lymph nodes) it is malignant (cancerous). The cancerous cells that have spread to other parts of the body are called metastases.

In a healthy adult body, cell growth and death is controlled so that there is always approximately the same number of cells in the body. Sometimes cells start dividing and growing uncontrollably and continue to grow even when the body does not need more of that type of cell. This cluster of extra cells is called a tumour.

Benign tumours are not considered a serious medical problem unless they interfere with normal surrounding tissue. For example, sometimes a benign tumour is so big that it gets in the way of tissue around it. In these cases, the tumours may be removed.

How does cancer spread?

Cancer cells can spread to other tissues in two ways: 

• Invasion: the cancerous cells spread by growing into nearby tissues and organs
• Implantation: the cancer cells spread to tissues and organs that are further away through the blood stream or lymphatic system. This more advanced stage of cancer is called metastasis

The original cluster of abnormal cells is called the primary tumour. When the cancer spreads to another area of the body, this second tumour is called a secondary tumour.

Some malignant primary tumours stay in their original location, and don’t spread, for relatively long periods of time. For example, prostate cancer is generally slow growing and does not spread outside the prostate quickly. This is good news because it means that if caught early, most men will be cured.