What does the term "metastasis" refer to?

The term "metastasis" specifically refers to the process by which cancer cells spread from the primary site of the tumor to distant parts of the body. This occurs when cancer cells break away from the original tumor, travel through the bloodstream or lymphatic system, and establish new tumors in other organs or tissues. Metastasis is a critical aspect of cancer progression and is associated with an increase in the severity of the disease, often complicating treatment and impacting patient prognosis.

The other choices describe related concepts but do not accurately capture the definition of metastasis. For instance, the growth of a new tumor does not necessarily imply it has spread from another site, and the formation of a secondary tumor at the original site refers to local recurrence rather than metastasis. Similarly, the treatment of cancer is a separate topic entirely and does not define metastasis itself. Understanding the specific definition of metastasis is crucial in the context of cancer biology and treatment strategies.