What does cancer metastasis refer to?

Cancer metastasis specifically refers to the spread of cancer cells from the original (primary) tumor site to other parts of the body. This process can occur through the bloodstream or lymphatic system, allowing cancer cells to invade new tissues and form secondary tumors. Understanding metastasis is crucial in cancer research and treatment, as it significantly impacts the prognosis and management of cancer patients. Identifying and targeting metastatic cells becomes a central focus in developing therapies that aim to prevent or reduce the spread of cancer, thereby improving patient outcomes.

In contrast, the primary growth of cancer cells is limited to the original site, the shrinking of tumors after treatment indicates a positive response to therapy, and the cessation of cancer cell division would imply that cancer is no longer proliferating, rather than spreading. Thus, option B accurately captures the critical nature of metastasis in the context of cancer progression.