Sarah Harding, 38, told her fans on Twitter that she was diagnosed with breast cancer earlier this year.
The cancer has since spread to other parts of her body, and she's now undergoing chemotherapy, she explained.
Sarah wrote on Twitter: " Hi everyone, 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."
More to follow...