Former President Jimmy Carter, who is both a pre-eminent citizen of Georgia and a history-making figure in international public health, announced Wednesday that he has cancer.

Carter, 90, had surgery earlier this month to remove a small mass from his liver. Tests showed that it was malignant and that the cancer had spread to other parts of his body, he said in his announcement. He will be cutting back his travel schedule to remain in Atlanta for treatment at Emory Healthcare, he added.

Before serving as president from 1977 to 1981, Carter was a naval officer, a South Georgia peanut farmer, a state legislator and governor of Georgia. Since leaving the White House, he has devoted himself to peace and philanthropy. He founded the Carter Center in Atlanta in 1982 and won the Nobel Peace Prize in 2002.

Among other projects around the world, Carter and the Carter Center have promoted public health as a way to increase prosperity and advance peace. He is the individual most identified with the campaign to eradicate guinea worm, a tropical disease caused by parasites in drinking water.

The Carter Center is a key forum for discussions of health policy in all its aspects.

Carter has been involved in anti-cancer efforts for years, and has spoken publicly about the toll the disease took on his family. All three of his siblings died of pancreatic cancer, as did his father, and he lost his mother to breast cancer.

Though several presidents had close ties to Georgia — including Franklin D. Roosevelt, who died in Warm Springs in 1945 — Carter is the only native of the Peach State ever to hold the nation’s highest office.

Carter is one of four living former presidents. He and the oldest member of the group, George H.W. Bush, were born a few months apart in 1924. Coincidentally, the other two living former presidents, Bill Clinton and George W. Bush, were born about a month apart in 1946.

In a statement, President Obama wished Carter a quick recovery.

“Our thoughts and prayers are with Rosalynn and the entire Carter family as they face this challenge with the same grace and determination that they have shown so many times before,” Obama said. “Jimmy, you’re as resilient as they come, and along with the rest of America, we are rooting for you.”