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Howard Stern sidekick Robin Quivers revealed why she hasn't been in the studio this past year: she was battling cancer.

Quivers made the startling admission on Howard Stern's Sirius XM radio show today, adding that she's now cancer-free.

The 61-year-old said she underwent treatment, including radiation and chemotherapy, for cancer that started in the endometrial tissue of her uterus. She added that doctors told her three months ago she's "cured."

"I gotta be honest, I thought she was a goner," Stern told listeners today, adding that he still gets chills hearing Quivers' story. "I can't tell you how dire everything seemed."

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Quivers said doctors found a tumor in her pelvis in May.

Even while going through two surgeries and months of radiation and chemotherapy, Quivers continued to do Stern's radio show from home, missing only two days on the air.

"I was so flabbergasted," Stern said. "She said the show was the only thing that gave her solace."

"It never occurred to me not to be on the air," Quivers said. "When I was on the air, I was pain-free."