What does the term "metastasis" refer to in cancer biology?

The term "metastasis" in cancer biology specifically refers to the process by which cancer cells spread from their original (primary) site to other parts of the body. This can occur when cancer cells detach from the primary tumor, travel through the bloodstream or lymphatic system, and form new tumors in distant organs or tissues.

Understanding metastasis is crucial in cancer biology because it significantly affects the prognosis and treatment options for patients. The ability of cancer to metastasize is a key factor in its severity, as it can lead to the development of secondary cancers that complicate treatment and decrease survival rates.

In contrast, the growth of a primary tumor describes the initial development of cancer in its original location and does not involve the movement of cells to other sites. The measurement of tumor size pertains to assessing how large the cancerous growth is but does not reflect the behavior of the cancer in spreading. Similarly, the type of treatment used for localized cancer deals with managing cancer confined to its original site and does not address the complex dynamics of metastasis. Therefore, the term primarily focuses on the spread of cancer cells, making it integral to understanding how cancer progresses in the body.