Cancer metastasis is the process by which cancer cells spread from the original tumor to other parts of the body. This occurs when cancer cells break away from the primary tumor, travel through the bloodstream or lymphatic system, and form new tumors in other organs or tissues. Metastasis can make cancer more difficult to treat and can lead to more severe health complications. Common sites for metastasis include the lungs, liver, bones, and brain. Early detection and treatment of the primary tumor can help reduce the risk of metastasis and improve patient outcomes.