Former President Jimmy Carter (90 years old) announced he has been diagnosed with cancer. Cancer is widespread, but not yet clear what kind of cancer he has. It was discovered after a procedure on his liver earlier this month. Carter announced on Aug. 3 that he had surgery to remove a small mass from his liver. "Recent liver surgery revealed that I have cancer that now is in other parts of my body," Carter said in the statement released by the Carter Center. "I will be rearranging my schedule as necessary so I can undergo treatment by physicians at Emory Healthcare." The liver is often a place where cancer spreads and less commonly is the primary source of it.

James Earl Carter Jr. was 39th president of the United States, from 1977 to 1981. He's kept active despite his age, working with groups such as Habitat for Humanity, winning the Nobel Peace Prize in 2002 and founding the nonprofit Carter Center in his home state of Georgia. Maybe pancreatic cancer? Carter's family has a history of pancreatic cancer. His father, both his sisters and his brother died of pancreatic cancer, and his mother had pancreatic cancer as well.

Pancreatic cancer can spread to other organs, including the liver, and cancer can also originate in the liver and spread elsewhere. However, when cancer spreads from one organ to elsewhere in the body, it is considered Stage IV cancer -- the most advanced stage. Stage IV cancer is generally incurable, although it can be treated, depending on the type.

In 2007, Carter told The New York Times that he had CT scans twice a year and later MRI (magnetic resonance imaging) to look for tumors in his pancreas. Doctors say a 90-year-old patient cannot tolerate the same treatment that could buy years of life for cancer patients in their 60s or 70s.