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.
"Cancer cells can be carried in the bloodstream or lymphatic system to other parts of the body. There they can start to grow into new tumours."
"In order to spread, some cells from the primary cancer must break away, travel to another part of the body and start growing there. Cancer cells don't stick together as well as normal cells do. They may also produce substances that stimulate them to move. "
"The circulating blood sweeps the cancer cells along until they get stuck somewhere. Usually they get stuck in a very small blood vessel called a capillary."