In this section What is cancer? Cancer is a disease of the
body's cells, which are the body's basic building blocks. Our
bodies constantly make new cells: to help us to grow, to replace
worn-out cells, or to heal damaged cells after an injury.
Normally, cells grow and multiply in an orderly way, but
sometimes something goes wrong with this process and cells grow
in an uncontrolled way. This uncontrolled growth may develop
into a lump called a tumour. A tumour can be benign (not cancer)
or malignant (cancer). A benign tumour does not spread outside
its normal boundary to other parts of the body. However, if a
benign tumour continues to grow at the original site, it can
cause a problem by pressing on nearby organs. The beginnings of
cancer How cancer spreads A malignant tumour is made up of
cancer cells. When it first develops, this malignant tumour may
not have invaded nearby tissue. This is known as a cancer in-
situ (or carcinoma in-situ). As the tumour grows, it invades
surrounding tissue becoming invasive c