In a post on Twitter, the 60-year-old told fans she is to undergo surgery to have part of one of her lungs removed.
Kathy, who is famed for her stand up comedy as well as many acting roles, said she “should be up and running around as usual in a month or less” and will be “just fine”.
She wrote: “I’ve got to tell you guys something. I have cancer. I’m about to go into surgery to have half of my left lung removed.
“Yes, I have lung cancer even though I’ve never smoked!
“The doctors are very optimistic as it is stage one and contained to my left lung.
“Hopefully no chemo or radiation after this and I should have normal function with my breathing.
“I should be up and running around as usual in a month or less.
“It’s been a helluva four years, trying to get back to work, making you guys laugh and entertaining you, but I’m gonna be just fine.”
Kathy added that she has been vaccinated against Covid and “the consequences for being unvaccinated would have been even more serious”.
“Please stay up to date on your medical check-ups. It’ll save your life,” she urged her followers.