The procedure Sen. John McCain underwent last week for a blood clot near his eye revealed a cancerous primary brain tumor, according to his office.

The tumor is known as a glioblastoma and was associated with the clot, a release from his office said.

The American Brain Tumor Association says glioblastoma is a highly malignant cancerous tumor and it is aggressive.

Treatment options could include a combination of chemotherapy and radiation.

They will depend on the results of genetic testing on the removed tumor, said Dr. Joseph Zabramski from the Barrow Neurological Institute. Zabramski doesn’t know enough about McCain’s tumor specifically to comment on what his options are, but does have advice for the Arizona senator:

“To not give up,” Zabromski said. “Everyone is different and the prognosis is highly variable. I myself have many patients who are long-term survivors of this.”

The office's statement said doctors called his underlying health excellent aside from the tumor.

It's not clear when McCain will return to the senate.

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McCain's office also released the following statement:

"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 White House released the following statement about McCain from President Donald Trump:

"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."

McCain, a prominent Republican voice, has represented Arizona in the U.S. Senate since 1987. He was the GOP's presidential candidate in 2008.

He was a Navy captain and prisoner of war in the Vietnam War, earning several medals of recognition for his service.

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