Refers to a cell or tumor that is growing in an uncontrolled fashion and is threatening to life (in other words, cancer, or "malignant tumor"). Malignancies have a tendency to metastasize (spread to other parts of the body) easily, making the treatment difficult and resulting in poor chances for survival. A tumor that is NOT malignant is called benign or non-malignant. Additional Info: There are many risk factors and many causes of cancer. Some of these are known, and many more aren't. At least one out of four people will develop some form of cancer during their lifetime, some of the most common ones being prostate cancer and non-malignant skin cancers. The single best prevention for cancer is to not use tobacco products. Of course, there are many other components to a healthy life style that reduce your risk of cancer such as proper diet and exercise. MSDS Relevance: If the MSDS says that a substance can cause malignancies, treat it with the utmost care and respect. Malignant cancers are ultimately fatal in the vast majority of cases. Avoid the use of the material if at all possible, especially if you have other risk factors for a particular kind of cancer (family history, being overweight, smoking etc Consider replacing the material with one that is not carcinogenic; there are often other available alternatives that work just as well. If you must use the material, utilize proper engineering controls such as a fume hood or other local exhaust ventilation as well as proper personal protective equipment such as gloves and respirators. See also: Carcinogen, Cytotoxin, Carcinoma, Metastasis