The younger Karl was diagnosed with the cancer in January but he decided to wait until the end of the basketball season to go public with the news. He is to be operated on April 2.
In March 2006 he had his thyroid removed. A statement by Boise State officials said it is not unusual for patients to need to second surgery of this type and that Karl's prognosis for recovery is excellent.
Karl said he plans to play in the NABC All-Star game March 31 during Final Four weekend in Atlanta.
He just completed his senior season at Boise State, earning All-Western Athletic Conference honors after averaging 14.8 points and 4.1 rebounds a game.