She was recently diagnosed with an early form of breast cancer detected at a routine mammogram screening, the spokesperson said.
The duchess was advised to undergo surgery and has done so successfully. She is now recuperating with her family.
The spokesperson said: “The duchess is receiving the best medical care and her doctors have told her that the prognosis is good.
“The duchess wants to express her immense gratitude to all the medical staff who have supported her in recent days.
“She is also hugely thankful to the staff involved in the mammogram which identified her illness, which was otherwise symptom-free, and believes her experience underlines the importance of regular screening.”
It is understood that the duchess was treated at the private King Edward VII’s Hospital in London, which has treated members of the royal family for decades.
She recorded an episode of her new podcast, called Tea Talk, the day before she went into hospital.
The episode, in which she talks about her diagnosis, will be broadcast on Monday.
Fergie, 63, shared an Instagram post on May 15 announcing the venture, teasing that it was “about time we spilled the tea”.
The show’s synopsis promises “candid conversations” between the Duchess and her co-host Sarah Jane Thomson, entrepreneur and founder of children’s news platform First News.
