Girls Aloud Singer Sarah Harding Reveals She's Battling 'Advanced' Breast Cancer: 'I Am Fighting'

Girls Aloud star Sarah Harding is battling breast cancer.

The 38-year-old singer — whose former bandmate, Cheryl, has a 3-year-old son with One Direction star Liam Payne — shared news of her heartbreaking diagnosis on social media Wednesday alongside a selfie taken from her hospital bed.

"There's no easy way to say this and actually it doesn't even feel real writing this, but here goes," Sarah, 38, posted on her Twitter and Instagram accounts.

"Earlier this year I was diagnosed with breast cancer and a couple of weeks ago I received the devastating news that the cancer has advanced to other parts of my body.

"I'm currently undergoing weekly chemotherapy sessions and I am fighting as hard as I possibly can."

Sarah — who recorded four UK No. 1 singles with Girls Aloud after the band's 2002 formation on British talent show Popstars: The Rivals — added that she made the information public to "let people know what's going on," after her hospital stay was mentioned online.

Despite this, she said she also realized the news would be "shocking" for people to suddenly read.

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"My amazing mum, family and close friends are helping me through this, and I want to say a thank you to the wonderful NHS doctors and nurses who have been and continue to be heroes," the singer added.

"I am doing my very best to keep positive and will keep you updated here with how I'm getting on. In the meantime I hope you'll all understand and respect my request for privacy during this difficult time. Sending you all so much love….xx"

Cheryl, 37, responded to the news by posting a broken heart emoji on her official twitter page.

"It goes without saying that this is blindsiding," Nicola Roberts wrote on Twitter. "Sarah, you're so loved and supported."

Another bandmate, Irish singer Nadine Coyle, added on Sarah's Instagram post: "I love you!!!! You have always been able to achieve miracles when needed!! I am here for [you] all the way & always will be!!! ❤️❤️❤️❤️❤️👑👑👑⭐️⭐️⭐️"

The group's fifth member Kimberley Walsh left a comment on Harding's Instagram post, writing, "My heart is broken. You are so strong and brave and we are with you every step of the way."

While Girls Aloud enjoyed limited chart success in the U.S., the five-piece band was a musical phenomenon in the UK, recording 21 top 10 singles between 2002 and 2013 — the most for any female group in UK chart history.