Define metastasis in cancer.

Metastasis refers specifically to the process by which cancer cells spread from the original (primary) tumor to distant organs or tissues within the body. This is a critical aspect of cancer progression, as it signifies that the cancer has moved beyond its initial location and can lead to the formation of secondary tumors. During metastasis, cancer cells may invade surrounding tissues, enter the bloodstream or lymphatic system, and then establish new tumors in various parts of the body, such as the liver, lungs, bones, or brain. This capability is one of the hallmarks of cancer and is associated with an increased severity of the disease and a poorer prognosis.

Understanding metastasis is vital for developing appropriate treatment strategies, as managing secondary tumors often requires different approaches compared to treating a primary tumor.