Arizona Sen. John McCain has been diagnosed with brain cancer, his doctors said Wednesday, less than a week after he was hospitalized for removal of a suspicious blood clot over his left eye.

A statement from the Mayo Clinic in Phoenix, where McCain underwent the blood-clot surgery Friday, said he has been diagnosed with a glioblastoma, which the hospital’s information page calls an “aggressive type of cancer that can occur in the brain or spinal cord.” It went on to say that glioblastoma “can be very difficult to treat and a cure is often not possible.”

But the clinic statement also quoted McCain’s doctors as saying he was recovering from the surgery “amazingly well” and it said his underlying health is excellent. The family is reportedly considering treatment options that could include chemotherapy and radiation.

McCain’s office also released a statement saying the 80-year-old senator is in “good spirits” as he recovers at home in Arizona.

McCain’s daughter, Meghan, posted a note to Twitter on Wednesday in which she asked for prayers for the family as it deals with the “shock of the news” and the “anxiety of what comes next.” But she added that her father was the “most confident and calm” of all of them.

“The cruelest enemy could not break him. The aggressions of political life could not bend him. So he is meeting this challenge as he has every other,” her statement said. “Cancer may affect him in many ways: But it will not make him surrender. Nothing ever has.”

That resilience was echoed by Sen. Lindsey Graham, R-South Carolina, one of McCain’s closest friends in Congress, who was on the phone with McCain to get updates on his condition Wednesday night.

Graham told reporters that McCain said, “I’m gonna stay here a little bit longer, take some treatments and I’ll be back.”

Senate Republicans were working on health care legislation on Capitol Hill late Wednesday night when they heard of McCain’s diagnosis. Sen. John Hoeven, R-North Dakota, said the room reacted with “stunned disbelief” when Graham brought them the news.

Hoeven told reporters said the senators prayed for McCain, led by Sen. James Lankford, R-Oklahoma.

McCain’s absence from the Senate has played a role in Republicans’ ongoing struggle to repeal and replace the Affordable Care Act, with Senate Majority Leader Mitch McConnell announcing last week that he would delay a vote pending the Arizona Republican’s return to Washington.

That plan appeared to fall apart this week when other GOP senators withdrew support for the proposed ACA replacement, and McConnell announced that the Senate would instead vote on a simple repeal of Obamacare. But the closed-door meeting of Republican senators last night was an attempt to bring a replacement bill back into play, which could make a McCain vote critical again.

McCain’s office said his return to Senate business depends on consultations with his doctors.

But while he has been recuperating in Arizona, McCain has not been detached from Washington politics. He issued a statement Monday, after the apparent collapse of the replacement effort, calling on senators on both sides of the aisle to take a step back, drafting a bill from scratch out in the open.

Glioblastoma is the same variety of cancer that killed Sen. Ted Kennedy, D-Massachusetts, in 2009. Kennedy was diagnosed in 2008 after a seizure.

According to the American Cancer Society, glioblastoma tumors are a fast-growing category of brain tumors that begin in the glial cells, which surround the central nervous system.

After news of McCain’s diagnosis broke, the senator received an outpouring of support from friends and political foes alike.

Fellow Arizona Republican, Sen. Jeff Flake, said he spoke to McCain Wednesday night, saying, “Tough diagnosis, but even tougher man.”

Rep. Trent Franks, R-Glendale, tweeted his condolences.

“I have just learned about my friend John McCain’s diagnosis,” Franks said. “I pray for him and his family tonight. He is an American hero.”

Former President Barack Obama tweeted: “John McCain is an American hero and one of the bravest fighters I’ve ever known. Cancer doesn’t know what it’s up against. Give it hell, John.”

Many of the statements echoed Meghan McCain’s.

“He is a warrior at dusk, one of the greatest Americans of our age, and the worthy heir to his father’s and grandfather’s name,” she wrote. “But to me he is something more. He is my strength, my example, my refuge, my confidante, my teacher, my rock, my hero – my dad.”