Kate Middleton announces she has cancer, undergoing chemotherapy treatment

Princess Kate announced she's been diagnosed with cancer in a video message.

The Princess of Wales, 42, has been undergoing preventative chemotherapy treatment after a planned abdominal surgery showed "cancer had been present." Kate did not elaborate on the form or extent of the cancer in her video.

She gave the update on her health Friday after undergoing major surgery earlier this year.

"I wanted to take this opportunity to say thank you, personally, for all the wonderful messages of support and for your understanding whilst I have been recovering from surgery," Kate said in the video recorded Wednesday.

"It has been an incredibly tough couple of months for our entire family, but I’ve had a fantastic medical team who have taken great care of me, for which I am so grateful."

KATE MIDDLETON'S MEDICAL RECORDS REPORTEDLY INVOLVED IN LONDON CLINIC SECURITY BREACH

Princess Kate announced she had been diagnosed with cancer in a pre-recorded video message shared Friday. (Getty Images)

"The Princess will return to official duties when she is cleared to do so by her medical team," a Kensington Palace spokesperson told Fox News Digital. "She is in good spirits and is focused on making a full recovery."

Meghan Markle and Prince Harry shared a message of support. "We wish health and healing for Kate and the family, and hope they are able to do so privately and in peace," a spokesperson for the Sussexes told Fox News Digital.

Meghan Markle and Prince Harry shared a message of support following the announcement of Kate Middleton's cancer. (Chris Jackson)

King Charles III said he is "so proud of Catherine for her courage in speaking as she did," according to a statement released by Buckingham Palace. He has kept in the "closest contact with his beloved daughter-in-law" during this time.

Kate's brother, James Middleton, took to Instagram on Friday to show his support for his sister and share an image with her from their childhood.

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"Over the years, we have climbed many mountains together. As a family, we will climb this one with you too," he wrote, adding the mountain and a red heart emoji.

The Princess of Wales explained that after her abdominal surgery, it was believed her condition was "non-cancerous." However, further testing showed "cancer had been present." She was advised to begin chemotherapy by her medical team.

The Princess of Wales said it took time to explain her illness to her kids, Prince George, Princess Charlotte and Prince Louis. (Jonathan Brady/AFP)

"This of course came as a huge shock, and William and I have been doing everything we can to process and manage this privately for the sake of our young family," she continued. "As you can imagine, this has taken time. It has taken me time to recover from major surgery in order to start my treatment. But, most importantly, it has taken us time to explain everything to George, Charlotte and Louis in a way that is appropriate for them, and to reassure them that I am going to be ok."

"As I have said to them; I am well and getting stronger every day by focusing on the things that will help me heal; in my mind, body and spirits," Kate added. "Having William by my side is a great source of comfort and reassurance too. As is the love, support and kindness that has been shown by so many of you. It means so much to us both."

Princess Kate said Prince William being by her side during this illness is a "great source of comfort." (Chris Jackson)

The princess asked for privacy as she completes treatment.

"We hope that you will understand that, as a family, we now need some time, space and privacy while I complete my treatment," she noted. "My work has always brought me a deep sense of joy and I look forward to being back when I am able, but for now I must focus on making a full recovery. At this time, I am also thinking of all those whose lives have been affected by cancer. For everyone facing this disease, in whatever form, please do not lose faith or hope. You are not alone."

Princess Kate is undergoing preventative chemotherapy. (Max Mumby/Getty Images)

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Kensington Palace confirmed to Fox News Digital on Thursday that Kate had been working from home during her recovery. She was being kept up to date regarding the Royal Foundation Centre for Early Childhood's trial of an observation tool for child development.

The Princess of Wales has remained out of the public eye since Dec. 25. Buckingham Palace later revealed she had been admitted to a hospital for a planned abdominal surgery on Jan. 17. Since then, she has only been spotted a handful of times, sparking speculation about her whereabouts.

Kate was most recently spotted walking through the Windsor Farm Shop nearly three months after her last official royal outing.

Kate has remained out of the public eye since Dec. 25. (Chris Jackson/Getty Images)

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On Mother's Day in the U.K., she shared a photo featuring her three children with Prince William — Prince George, Prince Louis and Princess Charlotte. The picture quickly became news as it was likely intended to quell speculation about the princess. However, the photo only fueled speculation about her health and whereabouts when it came to light that the image had been altered.

AP News issued a "photo kill" notice on a picture of Princess Kate and her children she released to the public. (AP News)

The princess later apologized on Instagram, writing: "Like many amateur photographers, I do occasionally experiment with editing. I wanted to express my apologies for any confusion the family photograph we shared yesterday caused."

"We don't have anything to add," the palace told Fox News Digital when asked for comments about the digitally altered photo.

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The Associated Press contributed to this report.