The word 'cancer' is the term for a group of different diseases - haematological (blood) cancers and solid tumours - which include malignant tumours of different sites in the body. There are over two hundred different kinds of cancer that can develop in almost any organ or tissue, such as your lungs, colon, breast, skin, bones or nerve tissue.

Most cancers are named after the organ or type of cell in which they originate and are characterised by the uncontrolled growth of abnormal cells.

Main cancer categories

According to CANSA, cancers are classified into six major categories based on tissue types:

• Carcinomas originate from the epithelial layer of cells that form the lining of external parts of your body or the internal linings of organs within your body
• Sarcomas originate in connective and supportive tissues including your muscles, bones, cartilage and fat. Bone cancer or osteosarcoma mostly affects young people
• Myelomas (a form of blood cancers) originate in the plasma cells of bone marrow that produce various antibodies in response to infections
• Leukaemia is a group of cancers that are classified as blood cancers. These cancers affect the bone marrow where blood cells are produced. When cancerous, the bone marrow begins to produce excessive immature white blood cells that fail to perform their usual actions and you're often prone to infection
• Lymphomas are cancers of the lymphatic system. Lymphomas may be of two types - Hodgkin's lymphoma and Non-Hodgkin's lymphomas. In Hodgkin's lymphoma there is characteristic presence of specific cells in the tissue samples which are not present in Non-Hodgkin's lymphoma
• Mixed types have two or more components of the cancer.