What is Cancer?

Our bodies are made of trillions of tiny cells. Normally, cells grow, divide and are replaced in an orderly way. Cancer is the name for a large group of diseases in which some cells start to grow out of control and can spread to other parts of the body.

Cancer can start almost anywhere in the body, and it can affect people of any age.

Cancer develops when changes (mutations) build up in a cell's genes — the instructions that tell it when to grow, divide and die. These changes can be caused by things around us, such as tobacco smoke or some infections, by ageing, or sometimes by genes passed down in families.

Damaged cells may keep dividing when they should stop. Over time they can form a mass, invade nearby tissue and, in some cases, travel through the blood or lymph system to other parts of the body. This spread is called metastasis.

There are more than 100 types of cancer, usually named after where they start. The main groups are:

• Carcinomas — start in the skin or the lining of organs, e.g. breast, prostate, lung, colorectal and cervical cancer.
• Sarcomas — start in bone, muscle, fat or other connective tissue.
• Leukaemias — cancers of the blood-forming tissue, such as bone marrow.
• Lymphomas and myeloma — start in cells of the immune system.
• Brain and spinal cord tumours — start in the central nervous system.

In Nigeria, the most commonly diagnosed cancers include breast, prostate, cervical, colorectal and liver cancer.

Only a doctor, usually with tests such as a biopsy, can tell whether a lump is benign or malignant.

A risk factor increases the chance of developing cancer. Having one does not mean you will get cancer. Common risk factors include:

• Tobacco use, including smoking and second-hand smoke
• Drinking alcohol
• Unhealthy diet, physical inactivity and excess body weight
• Certain infections, such as HPV, hepatitis B and hepatitis C
• Exposure to harmful substances at work or in the environment, and air pollution
• Too much sun (ultraviolet) exposure
• Increasing age and family history of some cancers

Symptoms depend on the type of cancer. Many of these signs are usually caused by other, less serious conditions — but they should be checked:

• A new lump or swelling, for example in the breast, neck or armpit
• Unexplained weight loss or loss of appetite
• Tiredness that does not go away
• A sore or wound that does not heal
• Unusual bleeding or discharge — in urine, stool, cough or between periods
• A cough or hoarse voice lasting more than three weeks
• Changes in bowel or bladder habits that last
• Difficulty swallowing or persistent indigestion
• Changes to a mole or skin patch
• Persistent pain with no clear cause