Congressman John Lewis of Georgia announced Sunday that he has stage IV pancreatic cancer, vowing he will stay in office and fight the disease with the tenacity which he fought racial discrimination and other inequalities since the civil rights era.

Lewis, 79, the youngest and last survivor of the Big Six civil rights activists in a group once led by the Rev. Martin Luther King Jr., said in a statement that cancer was discovered this month during a routine medical visit.

He said subsequent tests confirmed the diagnosis of stage IV pancreatic cancer.

'I have been in some kind of fight – for freedom, equality, basic human rights – for nearly my entire life. I have never faced a fight quite like the one I have now.

Congressman John Lewis of Georgia announced Sunday that he has stage IV pancreatic cancer. He is seen above on December 6 speaking at an event before the passage of the Voting Rights Advancement Act to eliminate potential state and local voter suppression laws, at the Capitol in Washington

In this February 15, 2011, file photo, President Barack Obama presents a 2010 Presidential Medal of Freedom to Lewis

Lewis speaks at a meeting of the American Society of Newspaper Editors, Washington DC, on April 6, 1964. He is sometimes called the 'conscience of the Congress' and is known for the prominent role he held during the 1960s civil rights struggles

'This month in a routine medical visit, and subsequent tests, doctors discovered Stage IV pancreatic cancer. This diagnosis has been reconfirmed.

'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.

'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.

'To my constituents: being your representative in Congress is the honor of a lifetime. I will return to Washington in coming days to continue our work and begin my treatment plan, which will occur over the next several weeks. I may miss a few votes during this period, but with God's grace I will be back on the front lines soon.

'Please keep me in your prayers as I begin this journey.'

The American Cancer Society estimates three per cent of patients with stage 4 pancreatic cancer are alive five years after being diagnosed.

Lewis - an Atlanta Democrat who is sometimes called the 'conscience of the Congress' - is known for the prominent role he held during the 1960s civil rights struggles.

In that era, he led hundreds of protesters in the 1965 Bloody Sunday march across the Edmund Pettus Bridge in Selma, Alabama.

Then 25, Lewis was at the head of the marchers when he was knocked to the ground and beaten by police.

Lewis (light coat, center), attempts to ward off the blow as a burly state trooper swings his club at Lewis' head during the attempted march from Selma to Montgomery in 1965. Lewis was later admitted to a local hospital with a possible skull fracture

Freedom Riders Lewis (left) and James Zwerg (right) stand together after being attacked and beaten by pro-segregationists in Montgomery, Alabama, in 1965

His skull was fractured, and nationally televised images of the brutality forced the country's attention on racial oppression in the South.

Lewis also joined King and four other civil rights leaders in organizing the 1963 March on Washington.

There he spoke to the vast crowd just before King delivered his famed I Have a Dream speech.

Lewis turned to politics in 1981, when he was elected to the Atlanta City Council. He first won a seat in Congress in 1986 and has served since.

Lewis stands on the Edmund Pettus Bridge in Selma, Alabama, in between television interviews in 2015. Lewis was beaten by police on the bridge on 'Bloody Sunday' on March 7, 1965, during an attempted march for voting rights from Selma to Montgomery

House Speaker Nancy Pelosi sent her best wishes to Lewis after the announcement of his illness and shared a snap with him

Lewis was among a group of Democratic lawmakers to skip Trump's inauguration in January 2017, saying he saw his election as illegitimate.

In response, the president-elect tweeted that Lewis should 'spend more time on fixing and helping his district, which is in horrible shape and falling apart (not to mention crime infested)', a remark drawing widespread criticism.

Prominent Democrats showed their support for Lewis following his announcement, with former president Barack Obama tweeting, 'If there's one thing I love about (Lewis), it's his incomparable will to fight. I know he's got a lot more of that left in him.'

House Speaker Nancy Pelosi also sent her best wishes to Lewis after the announcement of his illness.

'We are all praying for you following this diagnosis. John, know that generations of Americans have you in their thoughts & prayers as you face this fight.'

She said in a statement. 'We are all praying that you are comfortable. We know that you will be well.'