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 distant organs or tissues. Metastatic cancer can be more challenging to treat than localized cancer, as it often affects multiple areas of the body. The ability of cancer cells to metastasize is a key characteristic that distinguishes malignant tumors from benign ones. Common sites for metastasis include the lungs, liver, bones, and brain. Understanding metastasis is crucial for developing effective cancer treatments and improving patient outcomes.