What is cancer?
Cancer is a disease of the cells, which are the body’s basic building blocks. The body constantly makes new cells to help us grow, replace worn-out tissue and heal injuries. Normally, cells multiply and die in an orderly way.
Sometimes cells don’t grow, divide and die in the usual way. This may cause blood or lymph fluid in the body to become abnormal, or form a lump called a tumour. A tumour can be benign or malignant.
Benign tumour – Cells are confined to one area and are not able to spread to other parts of the body. This is not cancer.
Malignant tumour – This is made up of cancerous cells, which have the ability to spread by travelling through the bloodstream or lymphatic system (lymph fluid).
How cancer starts
Boundary Lymph vessel
Abnormal cells multiply
Malignant or invasive cancer
The cancer that first develops in a tissue or organ is called the primary cancer. A malignant tumour is usually named after the organ or type of cell affected.
A malignant tumour that has not spread to other parts of the body is called localised cancer. A tumour may invade deeper into surrounding tissue and can grow its own blood vessels in a process known as angiogenesis.
If cancerous cells grow and form another tumour at a new site, it is called a secondary cancer or metastasis. A metastasis keeps the name of the original cancer. Mesotheliomas form metastases only in the later stages of the disease process. They usually spread by invading nearby organs and structures in the chest and abdomen, and spreading to the lymph nodes in the chest.
How cancer spreads
Primary cancer Local invasion
Angiogenesis – tumours grow their own blood vessels
Metastasis – cells invade other
parts of the body via blood vessels and lymph vessels