The award-winning TV writer and actress, who is being treated for lung cancer related to a genetic form of the disease, joked about it being the third time she has faced the disease.
Aherne said: "My brother and I were born with cancer of the eyes, the retina. My mum told us only special people get cancer. I must be very special because I have had it in my lungs and bladder as well."
The comedian gave a typically irreverent speech as she spoke to a gathering of 170 cancer patients, medics and carers at Manchester Town Hall at the launch of a new cancer care scheme.
The 50-year-old star also described her own Macmillan cancer nurse, Julie Watts, as "like an angel".
The £3.4 million Macmillan Cancer Improvement Partnership aims to improve cancer care in the city, where survival rates for the disease are 25% lower than average.