Sarah, Duchess of York urged her former brother-in-law King Charles to "keep fighting on" when she took to the stage in Palm Beach, Florida on Wedneday.
The Duchess, 64, gave a speech at The Breakers Hotel who hosted the Cancer Alliance of Help and Hope's Palm Beach charity event. During her impassioned monologue, which has since been shared on social media, Sarah shared a touching tribute to the King as she thanked the charity for supporting her family.
She was also diagnosed with melanoma in January following her battle with breast cancer last year.
Sarah said: "I want to thank you all for your kindness in supporting my family members who are going through a hard time, and we wish everyone well, every family in the world, that has been diagnosed or who is going through a difficult time we wish them well.
"And of course, my brother-in-law, we wish you well, keep fighting on." The words were recorded by an audience member and shared on social media. The speech took place one day before she made her first public appearance since news of her cancer was revealed.
She added: "The cancer alliance is about hope, and there isn't enough hope in the world. For anyone who's suffering from low hope, for anyone who believes they can't do this, they can, it's absolute nonsense."
The Duchess of York credits her daughters Princess Beatrice and Princess Eugenie as being her strength during this challenging time. She told HELLO!: "They support me through thick and thin, not least my recent illness. We call each other 'The Tripod' because we prop each other up, come what may." Princess Beatrice is a patron of the British Skin Foundation and has worked with skin cancer patients.
Meanwhile, Sarah's touching message to Charles came just one day before Queen Camilla gave an update on the King's health during her first public engagement since the news broke of his cancer diagnosis.
The Queen confessed: "He’s doing extremely well under the circumstances, he's very touched by all the letters and the messages the public have been sending from everywhere – that’s very cheering."