Learning that a cancer has metastasized may be one of the scariest things you can hear from your doctor. Metastatic cancers are responsible for 90 percent of all cancer-related deaths. Here is an introduction to the fundamentals of how cancer develops and spreads.

Sunburns and excessive tanning can increase your risk for an aggressive form of skin cancer known as melanoma. Could other habits — such as medication use and even your profession — raise your melanoma risk as well?