Sen. John McCain, 80, has a brain tumor, the Mayo Clinic and the Arizona Republican's office announced Wednesday night.

"On Friday, July 14, Sen. John McCain underwent a procedure to remove a blood clot from above his left eye at Mayo Clinic Hospital in Phoenix," reads a statement from the Mayo Clinic, released at the request of McCain. "Subsequent tissue pathology revealed that a primary brain tumor known as a glioblastoma was associated with the blood clot. 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."

The statement continues, "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."

McCain's doctors say he is recovering from surgery "amazingly well" and "his underlying health is excellent," according to the statement.

According to the American Brain Tumor Association, more than 12,000 people a year are diagnosed with glioblastoma. The American Cancer Society puts the five-year survival rate for patients over 55 at about 4 percent.

Dr. David Farber, one of the doctors who cared for late Democratic Massachusetts Senator Ted Kennedy, has confirmed to ABC News that Kennedy's tumor was also glioblastoma.

President Donald Trump said in a statement, "Senator John McCain has always been a fighter. Melania and I send our thoughts and prayers to Senator McCain, Cindy, and their entire family. Get well soon."

The senator's office also issued a statement, which read, "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. Further consultations with Senator McCain's Mayo Clinic care team will indicate when he will return to the United States Senate."

The 2008 Republican presidential nominee's medical history includes four melanomas removed during three separate surgeries in 1993, 2000 and 2002. It is possible for melanoma to spread to the brain, which could explain why doctors scanned him and discovered the clot that required last week's surgery.

Senate Majority Leader Mitch McConnell issued a statement shortly after McCain's office announced he had the tumor.

"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. The entire Senate family’s prayers are with John, Cindy and his family, his staff, and the people of Arizona he represents so well. We all look forward to seeing this American hero again soon.”

Meghan McCain, the McCains' 32-year-old daughter tweeted, "The news of my father's illness has affected everyone one us in the McCain family."

Cindy McCain tweeted of Meghan McCain's full statement: "Her words are extraordinary."

McCain's Arizona counterpart in the Senate, Sen. Jeff Flake, R-Ariz. contributed his thoughts on the diagnosis via the social media platform as well, saying he recently spoke with McCain.

"Tough diagnosis, but even tougher man," wrote Flake.