How cancer spreads
Cancer cells can spread from where they started to other parts of the body, where they can grow into new tumours. This process is called metastasis.
Cancer can spread in 3 ways:
- invasion (direct extension) – The tumour grows into surrounding tissues or structures.
- through the bloodstream (hematogenous spread) – Cancer cells break away from the tumour, enter the bloodstream and travel to a new location in the body.
- through the lymphatic system – Cancer cells break away from the tumour and travel through the lymph vessels and lymph nodes to other parts of the body.
Where cancer can spread
The type of cancer and where it starts often influences if and where it will spread. The extent that cancer has spread when a person is diagnosed is called the stage. Many cancers follow a staging system from 0 to 4 (IV). Knowing how and where a cancer may spread helps doctors predict its possible course, plan treatment and further care.
These terms are also used to describe whether and how far cancer has spread:
- localized – The cancer is confined to the original site.
- regional spread – The cancer has grown into surrounding tissues or nearby lymph nodes.
- metastasis – The cancer has spread to a distant organ of the body or lymph nodes far from the original (primary) tumour.
It’s possible for cancer to spread anywhere in the body, but it’s most likely to go from its original site to other places in the body such as the bones, brain, liver or lungs.