What does metastasis refer to in a medical context?

Metastasis refers specifically to the process by which cancer cells spread from the primary tumor site to other parts of the body, establishing secondary tumors. This process can occur through various means, such as the bloodstream or lymphatic system, which allows these cancerous cells to invade tissues and organs that are distant from the original tumor. Understanding metastasis is crucial in cancer treatment and prognosis, as its occurrence often indicates a more advanced stage of disease. The other choices do not accurately capture the definition of metastasis in a medical context. For instance, the spread of infection pertains to infectious diseases rather than cancer, while the movement of bone cells relates to bone health and healing. Recovery from illness is associated with various medical conditions but is not related to the concept of metastasis at all.