Buckingham Palace, the headquarters of Britain's royal family, announced Feb. 5 that the 75-year-old monarch has begun regular treatment for cancer and has postponed all public engagements.
The palace confirmed the disease, which is not prostate cancer, was discovered while he was being treated in hospital for an enlarged prostate.
King Charles has started a schedule of regular treatments but has been advised "to postpone his public-facing duties." The palace declined to confirm the type of cancer.
In a post on social media site X, formerly Twitter, Cardinal Vincent Nichols of Westminster -- president of the bishops' conference of England and Wales -- expressed prayerful good wishes on behalf of Catholics.
"I am saddened to learn that King Charles is now facing a time of treatment for cancer," he wrote. "On behalf of the entire Catholic community in England and Wales, I offer His Majesty our warmest wishes and assurance of steadfast prayers for his full and speedy recovery."
"God bless the King," the cardinal concluded.
A royal spokesperson said the king will carry on working behind the scenes on state business and official papers.
Buckingham Palace said in a statement: "During The King's recent hospital procedure for benign prostate enlargement, a separate issue of concern was noted. Subsequent diagnostic tests have identified a form of cancer."
King Charles "commenced a schedule of regular treatments, during which time he has been advised by doctors to postpone public-facing duties," the palace said.
"The king is grateful to his medical team for their swift intervention, which was made possible thanks to his recent hospital procedure," the statement followed.
"He remains wholly positive about his treatment and looks forward to returning to full public duty as soon as possible," the statement added, saying that Charles had chosen to share the diagnosis "to prevent speculation and in the hope it may assist public understanding for all those around the world who are affected by cancer."
The king succeeded his mother, Queen Elizabeth II, on Sept. 8, 2022, when she died after a reign of almost 71 years, the longest-serving monarch in Britain's history. His coronation, in May 2023, was the first attended by papal representatives since the Protestant Reformation more than 500 years earlier. The processional cross used at the ceremony included fragments of the true cross gifted to King Charles by Pope Francis.