Introduction

This article will explain what is cancer, what causes it, what you can do to avoid it and how you can know if you might have it. A specialist in the treatment of cancer is called an ‘oncologist’.

What is Cancer?

Our bodies are made up of organs (e.g. liver, lungs, stomach, colon). In turn, these organs are made up of billions and billions of cells. Cells grow and when they become old or damaged, they die and are replaced with new cells. Normally, growth of new cells and death of old cells are kept in balance.
Cancer is a term which describes the uncontrolled growth of cells due to damage (mutation) in its DNA. So, instead of dying, damaged cells become immortal and continue to divide repeatedly and at a faster rate than normal (Figure 1). 

There are two main types of growths in the body: benign and malignant. Benign growths are not cancerous, do not spread to other parts of the body, and are therefore not life-threatening. By contrast, a malignant growth will continue to grow, and will spread to other parts of the body.

What are the different types of Cancer?

Cancer is not just one disease, but many hundreds of diseases. There are many different types of cancer. A cancer is termed after the organ it originates from. For example, a cancer originating in the lungs is termed ‘lung cancer’. Each cancer type can then be sub-divided into many different types. For example, there are over 50 different types of lung cancer, each of which behaves in a slightly different way, and so may require different treatments.
The body part that the cancer started from is called the primary cancer site and the places to which the cancer spreads (commonly, lungs, liver or bone), are called secondary sites (‘secondaries’ or more correctly, ‘metastases’).
Cancers that have spread to other parts of the body still look like the primary site under a microscope, and still behave like the primary cancer. Therefore, a cancerous deposit in the liver from a colon cancer is called ‘a secondary deposit (or metastasis) from primary colon cancer’ rather than ‘liver cancer’, and is treated in the same way as colon cancer not liver cancer.

Why is Cancer Dangerous?

Cancers are dangerous and must be treated as they will otherwise spread to other parts of the body. As cancers grow, they interfere with the normal working of the organ, and make patients weak and frail as they use up the body’s energy and nutrients to grow. Patients often therefore lose weight as the cancer grows.
Cancer spreads from its primary site to other parts of the body through the blood, the lymph system or by growing into a neighbouring organ.

Is  There a Cancer Epidemic?

Cancer is common, affecting 1 in 3 people. In general, there is no cancer ‘epidemic’, with only a very minor increase in cancer rates over recent years. This is probably because people are living longer. Therefore, our body’s cells have a longer time to become abnormal and immortal. Hence, it is not surprising that cancer is generally a disease of the elderly, and is rare in the young. This is a bit like a car. The older the car, the more likely the engine will develop a fault.