What does metastasis refer to in cancer biology?

Metastasis refers specifically to the process by which cancer cells spread from the original (primary) site of the 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 establish new tumors in distant organs or tissues. Metastasis is a hallmark of advanced cancer and significantly complicates treatment, as it can affect multiple sites within the body and is often associated with a poorer prognosis. Understanding metastasis is crucial in cancer research and treatment, highlighting the aggressive nature of certain cancer types that can spread beyond their initial location.