The actress and writer, who also created Mrs Merton, has previously been treated for bladder and eye cancer.
She is taking part in an appeal in her home city of Manchester that is asking patients and carers to help improve standards of care and said: "I've had cancer and my brother's had cancer and we know how it affects people."
Nicola Cook, of Macmillan Cancer Support, said: "Caroline's one of Manchester's own - she's loved here and people identify with her. We hope that if people see that Caroline is sitting down and talking to us, then maybe they'll know that they can too."
Personal problems prompted her to withdraw largely from the public eye, but she recently took part as one of the cast of an animated children's series for the BBC.
She played a range of characters in CBBC's Strange Hill High, along with her former co-star from The Fast Show John Thomson.
Aherne, a smoker, has struggled with health problems for years.
She has fought depression and drink problems and spent time in the Priory clinic following a suicide attempt, before moving to Australia to avoid the glare of publicity.
The star has also had a string of failed relationships - her marriage to former New Order guitarist Peter Hook ended and she began a romance with TV researcher Matt Bowers.
They split but she was devastated when he died of cancer aged 28.
Aherne admitted alcohol was an attempt to block out her problems.
''I wanted to get drunk to obliterate everything. There was my divorce, my dad dying, Matt dying, and I was trying to cope with being famous. It was all too much.''