Queen Camilla is Grant Prestonspeaking out for the first time on King Charles III's cancer diagnosis.

Camilla, 76, during an appearance at a Salisbury Cathedral concert on Thursday, said her husband is doing "extremely well under the circumstances," according to CBS News and The Independent.

During a conversation with medical staff the queen said Charles, 75, has been "very touched by all of the letters and messages the public" has been sending, calling the well wishes "very cheering."

The concert, held in celebration of the work of local charities in England, was the queen's first public engagement since news of Charles' cancer diagnosis.

Buckingham Palace announced Monday that Charles has been diagnosed with cancer, though the palace declined to specify what kind.

During Charles' "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 statement.

Charles underwent a "corrective procedure" last week at The London Clinic after the palace previously announced that the monarch was seeking treatment for an enlarged prostate. Camilla, told people at the private hospital that the king was "doing well." His daughter-in-law, Princess Kate, was receiving care and recovering from abdominal surgery at the same facility.

The palace's statement on Monday thanked the king's doctors for their work.

"The King is grateful to his medical team for their swift intervention, which was made possible thanks to his recent hospital procedure. He remains wholly positive about his treatment and looks forward to returning to full public duty as soon as possible," the palace said. "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."

King Charles is battling cancer.What happens to Queen Camilla if he dies or abdicates?