Your body is made up of different cells which are like building blocks and form all of the organs and tissues.
Cancer, derived from the word "crab" in Latin, is a disease where cells when they start to replicate and grow in an uncontrolled way. These abnormal cells clump together to form a lump which is called a "tumour".
There are more than 200 different kinds of cancer as they can originate from over 200 types of cell in the body.
Tumours can be examined under a microscope and described as benign or malignant.
Benign tumours are not as aggressive and only usually cause problems by pressing on surrounding areas or organs. Malignant tumours are more dangerous as they spread into normal tissues nearby and to other parts of the body via blood or the lymphatic system (part of the body's immune system).
Cancer is said to be "primary" (remained in its origin location) or "secondary or malignant" (spread elsewhere). For example, lung cancer - starts in the lung but can spread or "metastasise" to the liver and bone.
For more information, please see the websites citied on the page "Help and advice"
¿Cómo se desarrolla el cáncer?