Girls Aloud star Sarah Harding has said she has advanced-stage breast cancer.
The pop singer, 38, revealed the diagnosis on Twitter on Wednesday and said the disease had spread to other parts of her body.
Harding, born in Ascot in Berkshire, also shared a photo of herself in hospital.
There's no easy way to say this and actually it doesn't even feel real writing this, but here goes.
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.
She said: "I hope you are all keeping safe and well during these uncertain times. I've not posted on here for so long, thank you to everyone who has reached out to check in on me, it really does mean a lot.
"I feel now is the right time to share what's been going on.
"There's no easy way to say this and actually it doesn't even feel real writing this, but here goes.
"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.
"I understand this might be shocking to read on social media and that really isn't my intention.
"But last week it was mentioned online that I had been seen in hospital, so I feel now is the time to let people know what's going on and this is the best way I can think of to do so."
Popstars the Rivals at the Zuma club in London.
(left-right) Nicola Roberts, Javine Hylton, Cheryl Tweedy, Kimberley Walsh, Sarah Harding and Nadine Coyle the remaing girls from Popstars : the Rivals at the Smash Hits T4 Poll Winners Party at the London Arena.
Popstars - The Rivals winners, Girls Aloud from left to right; Nicola Roberts, 17, Nadine Coyle, 17, Sarah Harding, 20, Cheryl Tweedy, 19, and Kimberley Walsh, 20, pose for photographers in front of their poster in east London.
Popstars: The Rivals winners, Girls Aloud, from left to right; Cheryl, Nicola, Kimberley, Nadine and Sarah perform in public for the first time on stage during G.A.Y at the Astoria in London.
Girls Aloud performing on stage during the Prince's Polo Concert, at the Royal County of Berkshire Polo Club in Windsor.
Girls Aloud pose for group shots backstage at the Box Live Show at the Birmingham National Indoor Arena
Girls Aloud arrive at the Warner Village West End in London, for the UK premiere of Legally Blonde 2: Red, White & Blonde.
Girls Aloud perform on stage during the Hebs Live and Loud Concert at Hampden Park, Glasgow.
Girls Aloud onstage during the Disney Channel Kids Awards 2004, held at the Royal Albert Hall, central London.
Girls Aloud arrive for the Disney Channel Kids Awards 2004, held at the Royal Albert Hall, central London.
Girlband Girls Aloud arrives for ITV 1's National Music Awards held at the Carling Apollo in Hammersmith, London.
Cheryl Tweedy from pop band Girls Aloud and Bryan McFadden from boy band Westlife during their guest appearance on MTV's TRL UK at the MTV Studios in Camden, north London.
Pop bands Girls Aloud and Westlife during their guest appearance on MTV's TRL UK at the MTV Studios in Camden, north London.
Pop band Girls Aloud and their mothers arrive for the premiere of 'Freaky Friday' at the Odeon, Kensington High St in west London. From left to right; Diane and Kimberley Walsh, Joan and Cheryl Tweedy, Nadine and Elizabeth Coyle, Nicola and Debbie Roberts and Marie and Sarah Harding.
Pop group Girls Aloud perform live on stage during the third annual Fox Kids Planet Live pop event, at the Ahoy Stadium in Rotterdam, The Netherlands.
Girls Aloud receive the Band Of The Year Award during the Glamour Women Of The Year Awards at Berkeley Square in central London - the first annual award ceremony held by the women's magazine.
Girls Aloud arrive at the GAY Bar in London's Old Compton Street.
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She also thanked her "amazing mum, family and close friends" as well as the "wonderful NHS doctors and nurses" who were attending her.
Harding formed Girls Aloud with Cheryl, Nadine Coyle, Nicola Roberts and Kimberley Walsh on ITV's Popstars: The Rivals in 2002.
Cheryl simply shared a broken heart emoji in response to the news.