Sen. John McCain speaks out after brain cancer diagnosis: 'I'll be back soon, so stand-by!'

Sen. John McCain on Thursday shared a quick update on Twitter following news that sent shockwaves through Washington that the former 2008 Republican presidential nominee had been diagnosed with brain cancer.

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

The retired Navy captain received an outpouring of support Wednesday night, including from four presidents — Donald J. Trump, Barack Obama, Bill Clinton and the elder George Bush.