Both sides of the political aisle are wishing U.S. Sen. John McCain the best after discovering the Arizona Republican has been diagnosed with a brain tumor.

The aggressive cancer was discovered after doctors removed a blood clot above his left eye last week.

Political leaders have come together to offer McCain best wishes.

McCain tweeted on Wednesday that he was disappointed he had to miss a press conference on waste in government spending:

But for now he is recovering at home. This brain tumor is called glioblastoma and it is deadly. The average survival time is around 14 months, even with treatment.

This kind of cancer took the lives of both political giant U.S. Sen. Ted Kennedy and Beau Biden.

On Twitter, Biden’s father, former Vice President Joe Biden tweeted:

President Donald Trump also shared his thoughts on Twitter:

And the former presidential candidate's daughter spoke about how "tough" her father is.

“It won’t surprise you to learn that in all this, the one of us who is most confident and calm is my father. He is the toughest person I know. The cruelest enemy could not break him. The aggressions of political life could not bend him. So he is meeting this challenge as he has every other. Cancer may afflict him in many ways: but it will not make him surrender. Nothing ever has,” said Meghan McCain.

McCain’s press office says the senator and his family are reviewing further treatment options, which may include a combination of chemotherapy and radiation.