King Charles III has been diagnosed with an undisclosed type of cancer and will postpone public-facing duties to undergo treatment, Buckingham Palace announced this week. The 75-year-old king will begin “regular treatments” immediately.

This diagnosis comes shortly after the king underwent a “corrective procedure” in late January.

“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,” Buckingham Palace said in a news release.

Representatives said Charles did not have prostate cancer, but no further details about his treatment or prognosis were released. The king returned to London this week to begin treatment.

“His Majesty has chosen to share his 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 news release said.

Indeed, the announcement of Charles’s diagnosis comes as a surprise to royal biographer and historian Sarah Gristwood, who told NBC News that the health status of the royal family has historically been kept quiet to “keep any sign of ordinary human fallibility behind closed doors.”

“When Charles’s grandfather, George VI, was very gravely ill, the severity of his condition was kept not only from the public but from the patient himself,” Gristwood said of King George, who died suddenly of lung cancer in 1952. “Those were the attitudes of the time. Happily, things have now changed.”

Charles ascended the throne last May after the death of his mother, Queen Elizabeth II, at age 96.

It is reported that Prince William will resume public duties for the first time since his wife, Catherine, had abdominal surgery last month for an undisclosed condition that a royal source told CNN was noncancerous.

Despite the king’s diagnosis, he “remains wholly positive about his treatment and looks forward to returning to full public duty as soon as possible.”