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What is cancer?
Cancer is not just one disease, but a collection of unique
conditions in which cells in the body become abnormal,
then grow and multiply out of control. Although this
is true of all cancer types, whether it is breast
cancer, leukemia, lymphoma, lung cancer, or any of
several other types, each cancer has unique characteristics
and is treated with a unique set of therapies.
In some types of cancers, when cells grow out of control
they usually form a mass, called a tumour. These
tumours not only enlarge locally, but also have the
potential to invade and destroy the normal tissue around
them and to spread to distant parts of the body. These
tumours are called malignant tumours or cancers.
Some tumours grow and enlarge only at the site where they
begin. These tumours are not cancerous, and are referred
to as benign tumours.
Distant spread of cancer occurs when malignant cells
become detached from the original (primary) tumour,
get carried to other parts of the body through the
blood or lymphatic vessels, and establish themselves
in the new site as an independent (secondary) cancer.
A tumour that has spread in this manner is said to have
metastasized. The secondary tumour (or tumours) is called a metastasis (or metastases).
Since cancer may develop in any tissue of any organ,
there are many different types of cancer.
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