Despite the procedure to treat squamous cell carcinoma, Karl is expected to be back on the bench for Friday's game.
"It was the size of a nickel," Karl said. "I just have to be careful for a week to 10 days."
Karl, one of only nine coaches with 1,000 NBA wins, has battled prostate cancer that was diagnosed in 2005 and neck and throat cancer found in 2010.
"Coach told me the other day," Kings general manager Vlade Divac said, according to The Bee. "I told him to take as much time as he needs. ... We probably won't know the results for a couple days."
Divac said Karl was not sure how long the procedure would take.
"Whether it's one hour, two hours, three hours," Divac said. "We have practice, and I told him, 'I'll be there. You have to just do your thing, and if you need more time, don't worry about it. I'll take care of it.'"
Karl had not missed time with the Kings this season beyond a loss at New Orleans in January due to food poisoning.
Serious doubts over Karl's future with the Kings surfaced last month after sources told ESPN's Marc Stein the team had decided to fire the veteran coach. But Karl pledged to make changes to address growing concerns within the organization about his defensive schemes and practice policies, and the Kings decided against dismissing him. Karl's job status also appeared tenuous in November after a much-publicized blowup with center DeMarcus Cousins.
The two got into an altercation during a timeout in Wednesday's loss that resulted in Cousins being suspended by the team for one game.
Karl has an estimated $10 million in guaranteed money left on his original four-year, $15 million contract with the Kings.
Information from The Associated Press was used in this report.