Republican Senator John McCain of Arizona has been diagnosed with brain cancer after checking into a hospital for a blood clot near his left eye. Doctors discovered a glioblastoma, a malignant brain tumor.

The tumor was discovered at the Mayo Clinic Hospital in Phoenix last Friday.

"The Senator and his family are reviewing further treatment options with his Mayo Clinic care team," a Wednesday evening statement from McCain's office read. Chemotherapy and radiation may be the next step, according to the statement.

Doctors said McCain recovered from surgery "amazingly well," according to McCain's office, and they added that McCain's "underlying health is excellent."

McCain's daughter, Meghan McCain, confirmed the news, which she called a "shock" in a statement released Wednesday evening.

"It is an experience familiar to us, given my father's previous battle with cancer," she said, adding, "It won't surprise you to learn that in all this, the one of us who is most confident and calm is my father."

McCain has previously overcome cancer. He revealed in 2008 during his presidential campaign that he had four malignant melanomas removed in surgeries in 1993, 2000 and 2002.

McCain's colleagues in Congress tweeted their support and prayers for the 80-year-old six-term US senator, who chairs the armed services committee. McCain was also a Navy pilot and prisoner of war during the Vietnam War.

.@SenJohnMcCain is a hero to our Conference and a hero to our country. pic.twitter.com/Ld2lQH1mMn — Leader McConnell (@SenateMajLdr) July 20, 2017

Heartbreaking news. I've traveled the world w @SenJohnMcCain. I learned a lot from him - first and foremost, there is no one tougher. pic.twitter.com/gPtHDW1RlE — Chris Murphy (@ChrisMurphyCT) July 20, 2017

To @SenJohnMcCain and his family: Kelley and I will pray for you and your family, and we hope for a full recovery for you. — Senator Rand Paul (@RandPaul) July 20, 2017

President Donald Trump said that he and First Lady Melania Trump send their thoughts and prayers. "Get well soon," the president wrote.

Melania and I send our thoughts and prayers to Senator McCain, Cindy, and their entire family. Get well soon. https://t.co/fONWVlmYyz — Donald J. Trump (@realDonaldTrump) July 20, 2017

Former President Barack Obama called McCain "one of the bravest fighters I've ever known," and tweeted, "Cancer doesn't know what it's up against."

John McCain is an American hero & one of the bravest fighters I've ever known. Cancer doesn't know what it's up against. Give it hell, John. — Barack Obama (@BarackObama) July 20, 2017

Democratic Senator Ted Kennedy of Massachusetts died of brain cancer after a 15-month battle in August 2009 at the age of 77.

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