King Charles has been diagnosed with a form of cancer, Buckingham Palace announced, BBC reports.
It is not prostate cancer, but was discovered during his recent treatment for an enlarged prostate.
The type of cancer was not revealed, but according to a palace statement, the king began “regular treatments” on Monday.
Buckingham Palace said the king “remains completely positive about his treatment and looks forward to returning to full public duty as soon as possible”.
He will postpone his public engagements and other members of the royal family are expected to help stand in for him during his treatment.
No details are known about the stage of the cancer.
Although he will pause his public events, the king (75) will continue in his constitutional role as head of state.
On Sunday, he was seen at a church service in Sandringham, where he waved to the crowd.
He had prostate surgery at a private London hospital more than a week ago.
The king decided to go public with information about his prostate treatment, with the aim of encouraging more men to undergo prostate examinations, the palace announced.