What does metastasis refer to in cancer?

Metastasis refers to the process by which cancer cells spread from the original (primary) site to new areas in the body, forming secondary tumors. This spread can occur through the bloodstream or lymphatic system. When cancer metastasizes, it means that the disease has progressed beyond its initial location, indicating a more advanced stage of cancer that can complicate treatment and management of the disease. The formation of new cancer sites as a result of metastasis often makes the cancer more difficult to treat, as the cancerous cells in these secondary locations may behave differently than those in the primary site. Understanding this term is crucial for comprehending how cancer progresses and the implications it has for diagnosis and treatment plans.