The spread of a disease (usually cancer) from an original site of infection to other parts of the body. Metastatis usually happens when cancer cells break off from the original (primary) tumor and travel through the blood vessels or lymph system to a new site. Metastatic is used to describe a cancer that has metastasized, e.g. "metastatic breast cancer". Metastases refers to two or more metastatic tumors. Do not confuse this term with metathesis which is complete unrelated. Additional Info: Metastatic cancers usually indicate a malignant primary cancer, one that is life-threatening and possibly incurable. The metastic tumor cells are generally like those at the original tumor site and can indicate the original site where the cancer first developed in the body. Some cancers metastasize easily and others do not. Factors that affect the likelihood of metastasis include the location, type, stage, and size of the original tumor. Some metastatic cancers can be successfully treated whereas others, such as most pancreatic and lung cancers, are generally fatal. MSDS Relevance: See: Malignant. This term is unlikely to appear on an MSDS except for a possible description of health effects such as "metastatic bone cancer" etc. See also: Carcinogen, Leukemia, Malignant