It's the second time the mum of three has been diagnosed with melanoma.
The 41-year-old went to the doctor with a mole on her arm.
She said in her podcast Telling Everybody Everything she was initially told it was not a problem.
A sample was taken and sent off for testing, which later confirmed it was cancer.
She added: “He [the doctor] rang me today and it did come back as melanoma. Early melanoma. The doctor was shocked and told me I need to go back.”
Canadian Ryan, who has appeared on 8 Out Of 10 Cats and Have I Got News for You? said she was glad she listened to her instincts.
She told listeners: “I know you should never Google things but I'm actually really worried.
“Normally I'm that positive person. I think it's really easy to ta...