"It was very, very small, so I got it very, very early which is incredibly lucky," she said
In a video posted to her Instagram account on Saturday morning, she said she was "very angry" when she found out but feels in a "much more positive place" following a lumpectomy.
She said: "I have had breast cancer. I found a lump a few weeks ago. It came and went but then I was working on The Masked Singer and Lorraine, the TV show, and Lorraine Kelly had put signs on the backs of all the doors saying 'check your breasts' and every time I went for a wee I did that.
"It was still there, and then one morning I saw myself in the mirror and thought 'I'm going to get that looked at'.
"I had a biopsy. I found out it was indeed breast cancer and I had it taken out in a lumpectomy nearly three weeks ago."
She added: "It was very, very small, so I got it very, very early which is incredibly lucky. But I am so relieved to have had it removed and to know that it hasn't spread. My lymph nodes were clear, I didn't have any removed, and all I'm going to do now is have five days of radiotherapy in January as kind of an insurance policy."
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McCall thanked medical staff who treated her and urged women to get their breasts checked.
She said: "I just want to say a massive thank you to everybody at the Royal Marsden (Hospital) … all the nurses, doctors who have helped me, thank you for your support.
"Thanks to my family, to my brilliant kids, and an extra special thanks to Michael (Douglas). It's been a lot. I was very angry when I found out, but I let go of that and I feel in a much more positive place now.
"I think my message is: get checked if you're worried. Check yourself regularly. If you are due a mammogram, then get it done.
"I have dense breasts and I had a mammogram in August, and I was postponing the ultrasound; I just couldn't find time to do it. Don't do that. Get the ultrasound."
