Cancer cells have to go through several steps to spread to new parts of the body:.

• They have to be able to break away from the original tumor and enter the bloodstream or lymph system, which can carry them to another part of the body.
• They need to attach to the wall of a blood or lymph vessel and move through it into a new organ.
• They need to be able to grow and thrive in their new location.
• They need to be able to avoid attacks from the body’s immune system.

American Cancer Society