Former Sen. Bob Dole announced Thursday morning he has been diagnosed with stage 4 lung cancer.

The 97-year-old former GOP senator and presidential nominee announced in a tweet that he will begin treatment on Monday.

“While I certainly have some hurdles ahead, I also know that I join millions of Americans who face significant health challenges of their own,” Dole said.

Dole served as a congressman and then senator from 1961 to 1996 from his home state of Kansas.

He spent his first eight years in Washington as a member of the House of Representatives before graduating to the Senate in 1969 and serving through 1996.

Dole’s involvement in presidential politics is as lengthy as anyone to never hold the office. He ran for president once, vice president once and twice came up short for the GOP nomination for president.

Dole was previously honored with the Presidential Medal of Freedom by former President Bill Clinton, just months after losing the presidential election to him.

In 2018, Congress awarded him the Gold Medal.

ABC News’ Mark Osborne contributed to this report.