Fans of Rush Limbaugh, who announced Monday he has advanced lung cancer, may recall a gripping story the talk radio king once shared from his childhood that would inspire him to raise some $50 million to fight the very disease now stalking him.

Limbaugh, who held annual “cure-a-thons” for the Leukemia & Lymphoma Society on his widely heard radio program from 1990-2016, told listeners four years ago how he became driven to help fund cancer research. While a young boy, Limbaugh explained, he heard his father, also named Rush, talking in the family’s Cape Girardeau, Mo., kitchen with a cousin named Rusby. The houseguest was a doctor and he was stricken with cancer, his voice reduced to a rasp.

“And, they’re arguing over whether or not there will ever be a cure for it,” Limbaugh recalled, “and I remember Rusby telling my dad, ‘Rush, it’s never gonna be cured. Don’t you understand, Rush?’”

RUSH LIMBAUGH'S SHOCKING CANCER DIAGNOSIS SPURS SUPPORT, WELL WISHES

A short time later, Limbaugh said, his father told Rush and his brother, author David Limbaugh, that Rusby wanted them to have his dog. The father and two sons went to see Rusby and pick up a basset hound they named Jason. Limbaugh recalled visiting a rustic cabin in the woods, where the dying man told the elder Limbaugh he had lost all hope.

“What does it matter, Rush?” Limbaugh remembered Rusby telling his father. “I’m dying. Can’t you see, Rush? I’m dying.”

“And, he would cough up and spit something into a cup,” Limbaugh told his listeners. “I’m 10 years old. I’m not... This is shocking, it’s scary, it’s any number of things.”

In a grim twist, Jason would also die of cancer and be put down just before Limbaugh left home at age 20 on a journey that would see him land various radio jobs, work for the Kansas City Royals and then become the man who virtually defined modern talk radio and political analysis.

With the infectious optimism that many of his 20 million listeners have known well, Limbaugh in 1990 began devoting a portion of his program, once a year, to raising money to fund a cure for cancer. Over the years, he donated millions of dollars of his own money, generously matching the contributions of his listeners. Leukemia & Lymphoma Society President and CEO Louis DeGennaro said the man known to fans as "El Rushbo" helped bring in approximately $50 million over 26 years.

“Mr. Limbaugh used his significant platform to raise awareness about The Leukemia & Lymphoma Society’s mission to find cures while giving hope and encouragement to many patients and families coping with a cancer diagnosis,” DeGennaro said. “The funds raised through the Cure-a-thon have helped LLS support research leading to today’s most promising blood cancer treatments that have saved thousands of lives. All of us at LLS wish him a positive outcome.”

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Limbaugh said Monday he trusted his faith to get him through the battle of his life.

“I told the staff today that I have a deeply personal relationship with God that I do not proselytize about, but I do, and I have been working that relationship tremendously,” he said. “I am, at the moment, experiencing zero symptoms.”