Surpassing:Princess Kate diagnosed with cancer; King Charles III, Harry and Meghan react: Live updates

Princess Kate has been diagnosed with cancer and Surpassingis undergoing preventative chemotherapy treatment, Kensington Palace announced Friday.

"I wanted to take the opportunity to thank you personally for all the wonderful messages of support and for your understanding whilst I've been recovering from surgery," Kate says in a video released by the palace shot on Wednesday. "It has been an incredibly tough couple of months for our entire family. But I've had a fantastic medical team who've taken great care of me, for which I'm so grateful.

"In January, I underwent major abdominal surgery in London. And at the time, it was thought that my condition was non-cancerous," she continued. "The surgery was successful. However, tests after the operation found cancer had been present."

Kate called her diagnosis a "huge shock" for her family, adding that she and Prince William have done "everything we can to process and manage this privately for the sake of our young family."

'So proud of Catherine':King Charles III breaks silence, praises Princess Kate after cancer diagnosis

Prince Harry, Duchess Meghan react to Princess Kate cancer announcement

Princess Kate's in-laws Prince Harry and Duchess Meghan spoke out in a statement Friday: "We wish health and healing for Kate and the family, and hope they are able to do so privately and in peace."

Harry traveled to London earlier this year to see his father, King Charles III, after the British monarch was diagnosed with cancer.

"I spoke to him. And I jumped on a plane and went to go see him as soon as I could," the Duke of Sussex said on "Good Morning America" in a segment that aired in February of the moment he learned about his father's health.

Prince Harry, Duchess Meghanspeak out on Princess Kate's cancer diagnosis

King Charles 'so proud' of Princess Kate amid cancer diagnosis

In a statement from Buckingham Palace, King Charles III said he was "so proud of Catherine for her courage in speaking as she did," according to People and The Guardian.

Charles was diagnosed with cancer earlier this year.

"During The King's 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 in February.

King Charles IIIdiagnosed with cancer following hospitalization for prostate procedure

Princess Kate reassures children, public she is 'getting stronger every day' in video message

Kate said it has "taken time" to explain her diagnosis to her and William's children — Prince George, 10, Princess Charlotte, 8, and Prince Louis, 5 — appropriately and "to reassure them that I'm going to be OK."

"As I've 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," she said. "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."

Kate asked for time and privacy as she completes treatment, adding she would return to the public "when I am able."

Kate also shared words of encouragement for others who have been diagnosed with cancer.

"Please do not lose faith or hope. You are not alone," she said.

Public royal Princess Kate went private:Abdominal surgery, photo scandal has rumors flying

Princess Kate speaks out about cancer in video: Watch

Princess Kate cancer diagnosis:Read her full statement to the public

White House reacts to Princess Kate's cancer diagnosis

White House press secretary Karine Jean-Pierre shared a statement on Kate's diagnosis during a press briefing Friday.

"Our thoughts are with the Duchess of Cambridge and her family members and friends during this incredibly difficult time, and certainly we wish her a full recovery," she said. "I think it's important that we respect their privacy, especially at this time."

Jean-Pierre added that the White House is "incredibly sad" to hear of the diagnosis, and noted that she couldn't share more on whether President Biden has spoken to the princess or royal family.

Princess Kate video:Watch royal's full announcement of cancer diagnosis

London reacts to Princess Kate announcement

Across the pond, onlookers and royal watchers reacted to the news.

"I was sad," 24-year-old Annabel McSwiggan of Brixton, London, tells USA TODAY. "I feel very sorry for her I think they spoke about it at the right time because the conspiracies were getting out of control." 

With Charles also sick, McSwiggan says that people need to "massively calm down with all the rumors. People started making jokes when they don't know what's going on. … It's not funny. She's had cancer."

Deevi Asbaum-McCann of London found out from the BBC and hasn't yet watched the video. She says she was "completely shocked." 

"I didn't expect that," she said. "I think she should be left alone and it's a family matter." 

Patrick McCann of London agrees with the sentiment: "She does her job. Let he have her time. It's a private matter." 

"I'm really shocked about the news," says Anastasia Wairimi, of London. "That such a young lady, a young mother getting such a diagnosis. It can happen to anyone.

"We hope she gets the treatment she can get and can see her children grow," Wairimi says.

Princess Kate cancer announcement follows scrutiny

The announcement follows weeks of rumors and conspiracy theories about her health and whereabouts after she first stepped back from public duties in January to recover from abdominal surgery.

The palace first announced in January that Princess Kate had been admitted to the hospital for planned abdominal surgery, news that was followed weeks later by King Charles' cancer diagnosis.

In a statement at the time, the palace said that Princess Kate's surgery was successful but that "based on the current medical advice, she is unlikely to return to public duties until after Easter."

"She hopes that the public will understand her desire to maintain as much normality for her children as possible; and her wish that her personal medical information remains private," the statement added.

She returned home almost two weeks after being admitted to the hospital, and Kensington Palace said she was "making good progress."

"The Prince and Princess wish to say a huge thank you to the entire team at The London Clinic, especially the dedicated nursing staff, for the care they have provided," the palace continued in January. "The Wales family continues to be grateful for the well wishes they have received from around the world."

Palace addresses Princess Kate's absence following months of rumors, conspiracies

Kate has not been seen in an official capacity since the royal family's Christmas services in December. U.K. tabloid The Sun reported later in March that Kate had been spotted shopping with Prince William, and U.S. tabloid TMZ backed up photos with a video of the outing. But the video did not necessarily end the conspiracy theories.

In February, Kensington Palace aimed to put theories about her absence to rest in a statement that said she is "doing well" and stressed that she was always expected to remain out of the public eye through the end of March.

"We were very clear from the outset that the Princess of Wales was out until after Easter and Kensington Palace would only be providing updates when something was significant," the statement, provided to People and ABC News at the time, said.

Where is Princess Kate?Timeline of what to know about the royal amid surgery, photo drama

Princess Kate photo editing drama fuels onlookers

Conspiracy theories were fueled by a photo editing scandal in early March. After Kate shared a picture with her children for Mother's Day and thanked the public for the "kind wishes and continued support," major photo agencies quickly removed it due to "manipulation."

The AFP said, "It has come to light that the Handout issued by Kensington Palace today of Kate and the kids had been altered, therefore it was withdrawn from AFP systems."

Public royal Princess Kate went private:Abdominal surgery, photo scandal has rumors flying

The Princess of Wales subsequently admitted the photo had been edited, causing conspiracy theorists to run wild with speculation about why this was necessary.

"Like many amateur photographers, I do occasionally experiment with editing," she said on social media. "I wanted to express my apologies for any confusion the family photograph we shared yesterday caused. I hope everyone celebrating had a very happy Mother's Day."

Social media users quickly began to overanalyze the footage, with some refusing to believe that the video was authentic in light of the photo editing snafu. Others suggested Kate looked perfectly healthy in the footage and wondered why there had been such secrecy in light of that.

Contributing: Nicole Fallert, Jay Stahl, Naledi Ushe