Sen. John McCain John Sidney McCainMomentum growing among Republicans for Supreme Court vote before Election Day McConnell urges GOP senators to 'keep your powder dry' on Supreme Court vacancy McSally says current Senate should vote on Trump nominee MORE (R-Ariz.) on Thursday thanked supporters for their well-wishes after he was diagnosed with brain cancer, promising to be back in Congress soon.

“I greatly appreciate the outpouring of support - unfortunately for my sparring partners in Congress, I'll be back soon, so stand-by!” McCain tweeted Thursday.

I greatly appreciate the outpouring of support - unfortunately for my sparring partners in Congress, I'll be back soon, so stand-by! — John McCain (@SenJohnMcCain) July 20, 2017

ADVERTISEMENT

The Mayo Clinic Hospital in Phoenix said Wednesday the Arizona senator was diagnosed with brain cancer after a tumor was discovered during a minor procedure last week to remove a blood clot from above his left eye.

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

“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 office said in a statement that he remained in good spirits Wednesday and is confident that any treatments will be effective.

“He is in good spirits as he continues to recover at home with his family in Arizona,” his office said. “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.”

Lawmakers from both parties took to Twitter to share their support and admiration for the senator.

McCain’s latest diagnosis is not his first battle with cancer, as he underwent a procedure in 2000 to remove a type of skin cancer from the left side of his face.