Georgia Rep. John Lewis has been diagnosed with stage 4 pancreatic cancer. On Sunday (Dec. 29), the civil rights icon shared the somber news.

“I have been in some kind of fight—for freedom, equality, basic human rights—for nearly my entire life,” he said, as reported by CNN. “I have never faced a fight quite like the one I have now.”

The longtime congressman further revealed that he had been diagnosed during a routine medical visit and that he will soon begin treatment for the cancer.

“While I am clear-eyed about the prognosis, doctors have told me that recent medical advances have made this type of cancer treatable in many cases, that treatment options are no longer as debilitating as they once were, and that I have a fighting chance,” he said.

Several politicians and political activists rushed to offer Lewis their condolences, remembering his passion and fighting spirit as a celebrated civil rights leader. House Speaker Nancy Pelosi, Rep. Veronica Escobar, Barack Obama and more reacted to the sad news on Twitter.

“If there’s one thing I love about [Rep. John Lewis], it’s his incomparable will to fight,” the former president wrote on Twitter. “I know he’s got a lot more of that left in him. Praying for you, my friend.”

Currently serving in his 17th term in the US House, Lewis was first known as a civil rights leader. As a chairman of the Student Nonviolent Coordinating Committee, he marked one of the “Big Six” leaders that organized the 1963 March on Washington. Joining forces with Martin Luther King Jr., Lewis played a key role in the Civil Right Movement and in ending segregation. He has previously said he was arrested over 40 times for his protesting efforts.

For his courageous achievements, Lewis has been the recipient of several honors, including the Presidential Medal of Freedom, bestowed by President Obama. Despite the diagnosis, Lewis says he’ll be back to work soon, following a treatment plan that he expects to take several weeks.

“So I have decided to do what I know to do and do what I have always done: I am going to fight it and keep fighting for the Beloved Community. We still have many bridges to cross,” he said. “I may miss a few votes during this period, but with God’s grace I will be back on the front lines soon.”