The Prince and Princess of Wales are "enormously touched" and "extremely moved" by the public's warmth and support following Catherine's cancer announcement.
The 42-year-old Princess revealed she was undergoing preventive chemotherapy in an emotional video message on Friday.
There has been a global outpouring of support, including from King Charles, the Duke and Duchess of Sussex, political figures and members of the public.
A Kensington Palace spokesperson said on Saturday: "The prince and princess are both enormously touched by the kind messages from people here in the UK, across the Commonwealth and around the world in response to Her Royal Highness' message.
"They are extremely moved by the public's warmth and support and are grateful for the understanding of their request for privacy at this time."
Words of support came from Harry and Meghan, the Duke and Duchess of Sussex, who said: "We wish health and healing for Kate and the family, and hope they are able to do so privately and in peace."
The form of cancer has not been disclosed, but the future queen began a course of "preventive chemotherapy" late in February, and is said to have a positive mindset for her recovery and is in good spirits, describing herself as "well and getting stronger every day". It came after Catherine spent two weeks in hospital in January after having what her office said at the time was successful, planned surgery for a non-cancerous but unspecified condition.
William and Catherine have focused on their children, taking the time to sensitively share the state of the princess's health with Prince George, Prince Charlotte and Prince Louis.
Hashtags including "WeLoveYouCatherine" and "GetWellSoonCatherine" were trending on X, formerly Twitter, and well-wishers visited Windsor in Berkshire, on Saturday.
It is understood the video message, recorded on Wednesday in Windsor, was released on the day William and Catherine's three children began their Easter school holidays, to take advantage of the break to shield them from coverage of their mother's health.