What does the term "metastasis" refer to?

The term "metastasis" specifically refers to the biological process in which cancer cells spread from the primary tumor site to other distant parts of the body, forming secondary tumors. This process involves several steps, including invasion of nearby tissues, entry into the bloodstream or lymphatic system, and colonization of new sites, where the cancer cells can proliferate. Understanding metastasis is crucial in oncology because it indicates the progression and severity of cancer, often affecting treatment strategies and prognosis. The term encompasses a much broader and critical range of implications than simply the local growth of cancer cells or the development of secondary tumors in the same location. Thus, the correct choice captures the essence of what metastasis entails.