Sen. John McCain, R-Arizona, has been diagnosed with a brain tumor, the Mayo Clinic said Wednesday in a statement released on behalf of the senator and his family.

"Subsequent tissue pathology revealed that a primary brain tumor known as a glioblastoma was associated with the blood clot," the Mayo Clinic said in the statement.

The Mayo Clinic said in the statement that “scanning done since the procedure (a minimally invasive craniotomy with an eyebrow incision) shows that the tissue of concern was completely resected by imaging criteria," or cut out

"The Senator and his family are reviewing further treatment options with his Mayo Clinic care team. Treatment options may include a combination of chemotherapy and radiation," it said.

McCain's office said in a statement that McCain, 80, is in good spirits.

"Senator McCain appreciates the outpouring of support he has received over the last few days. He is in good spirits as he continues to recover at home with his family in Arizona. He is grateful to the doctors and staff at Mayo Clinic for their outstanding care, and is confident that any future treatment will be effective," the statement said.

"Further consultations with Senator McCain's Mayo Clinic care team will indicate when he will return to the United States Senate," it said.

Republican Sen. Jeff Flake of Arizona said in a statement on Twitter that he has spoken to McCain. “Tough diagnosis, but even tougher man.”

The 5-centimeter blood clot was removed in a minimally invasive operation following an annual physical, the Mayo Clinic said. It said at the time that the procedure went “very well” and was successful.

McCain, chairman of the Senate Armed Services Committee, is regarded as a tell-it-like-he-sees-it voice open to crossing the aisle to reach bipartisan agreement.

McCain, a former Navy pilot, was shot down during the Vietnam War and was held as a prisoner of war for more than five years by the North Vietnamese.

He was taken prisoner in October 1967 after being shot down during a mission over Hanoi. He wasn't freed until March 1973, after the United States signed peace agreements with the North Vietnamese.

McCain’s captors tortured him and held him in solitary confinement. Still, he declined an offer of early release until those who had been at the prison longer than him were let go.

McCain has a history of melanoma, an aggressive form of skin cancer.

Senate Majority Leader Mitch McConnell, R-Kentucky, in a statement called McCain an American hero and said the entire Senate’s thoughts are with him.

"John McCain is a hero to our Conference and a hero to our country. He has never shied from a fight and I know that he will face this challenge with the same extraordinary courage that has characterized his life,” McConnell said. "The entire Senate family’s prayers are with John, Cindy and his family, his staff, and the people of Arizona he represents so well.”

House Minority Leader Nancy Pelosi, D-California, said on Twitter that McCain "is a hero, a patriot and a fighter" and said she was praying for his recovery and for his family.