Millions of Americans were shocked when conservative icon Rush Limbaugh announced on Monday that he's battling an advanced form of lung cancer.

"So, I have to tell you something today that I wish I didn't have to tell you. It's a struggle for me because I had to inform my staff earlier today," Limbaugh said. "I can't help but feel that I'm letting everybody down. The upshot is that I have been diagnosed with advanced lung cancer."

After being awarded the Presidential Medal of Freedom at the State of the Union earlier in the week, "America's Anchorman" was back to work on Friday. While sharing the behind-the-scenes story of his trip to Washington, D.C., to accept the award, "El Rushbo" said that he has received some good news from doctors.

'It's advanced lung cancer. But there's good news...'

"It's late stage. It's advanced lung cancer," Limbaugh said.

"But there's good news associated with the diagnosis and the treatment," he added without going into further details.

In a later segment, while speaking with a caller, Limbaugh noted he has "great doctors that have already discovered some interesting things that should facilitate treatment" of his disease.

The conservative radio legend also said he cannot tell the full story behind his invitation to the State of the Union, as doing so would reveal "medical details" he would rather keep confidential.

Now, I know many of you want to know the story of the State of the Union address on Tuesday night and how that all happened, and someday I hope to be able to tell you the entire story. I can't tell you the entire story now without divulging medical details that I, frankly, don't want to give. I don't want to give people an opportunity to start investigating and writing about and pronouncing opinions and this kind of thing. People know enough about what I have.

'I'm stunned'

However, Limbaugh did disclose some details of the phone call he received from President Donald Trump on Tuesday morning when the commander-in-chief invited him to his annual address to Congress.

I answered the phone, and they said, "Can you hold for President Trump?"

I said, "Yes."

"Rush! Rush! How you doing, buddy? Great to hear from you! Hey, look, what are you doing later today?"

I said, "Well, I have a serious medical procedure that's gonna start — all this — at 5 o'clock."

"Well, look, what's the doctor's name? I want to call him and have him delay it for a couple days 'cause I need you down here tonight."

I said (chuckles), "Uh… (chuckles) Mr. President, um… I'm stunned."

Limbaugh said the President told him: "Look, your health comes first; there's no question. But can't they just do half of what they're gonna do and then send you down here? Believe me, you don't want to miss this. It's gonna be great."

The conservative commentator said his wife strongly encouraged him to accept the president's invitation and immediately went to work planning their travel arrangements to Washington.