It's after suffering an injury on the show that she feared could've have meant losing a breast.
Anastacia was originally ruled out of the first dance off of the series after ripping scar tissue from her double mastectomy.
Speaking about the incident today, the singer told Loose Women: "Not doing the dance-off was purely because they didn't know if I had injured it so much I would lose it [her breast].
"It was a fear and I was terrified. There wasn't a doctor open on Sunday, so I was a mess on Sunday until Monday when I could go in and find out I wouldn't lose the breast."
And Anastacia revealed: "I would have left not dancing off, personally, but they had rules."
In the end the dance off was cancelled and the elimination result was decided by the public vote, seeing Anastacia survive and Melvin Doom go home.
She said: "I felt awful - I didn't want anyone to think I wouldn't have left personally, but they have rules and they had to go the vote. This is just not someone I am - I'm very much fair but I joined a show that has rules and I had to go with the vote.
"I think Brendan had a difficult time with it as well, he's a pro and he'd never experienced it before. You almost feel you need to dance-off if you're hurt and then once he found out it wasn't just a sore muscle, it was deep..."
Confirming she wouldn't take part in next year's Strictly tour, Anastacia added: "I am putting out a special project for my fans, I’m like Anaclaus... Santascia!"
Strictly Come Dancing is back next Saturday and Sunday night on BBC One.