Pop Star Anastacia Battles Cancer

May 2 -- "You can say what you want about me … try to do what you want to me, but you cannot stop me," she sings in one of her songs. They call her survivor chick. She's an international superstar, who's gone platinum multiple times, selling more than 10 million albums.

She's a sexy siren who has performed with Paul McCartney, Celine Dion and Elton John. She's pop star Anastacia, who seems to have it all but who's fighting the fight of her life.

"I'm pretty much just walking with one foot in front of the other and hoping that the journey, once I'm going through it, it'll be interesting to be able to talk about."

"You had to look at this and say, 'you know, this is a ticking time bomb,'" said Dr. Alexander Swistel.

Before that time bomb exploded, she had fame, travel adoring fans — until one gray day in January. Anastacia, only 34 years old, learned she had breast cancer.

"I wanted to get a breast reduction. And one of the things that I had to do for the pre-op was get a mammogram. And I was kind of perplexed by it. Because I was like isn't that what those old ladies get. Well, I go in for that mammogram and three and a half hours later, my doctor is sort of sitting me down and kind of letting me know that they found something," she said.

What they found were tiny calcium spots, which can indicate cancer. In her attempt to have her double DD cup breasts reduced because of back pain, Anastacia had stumbled upon something far more serious.

‘I've Never Been This Afraid’

Anastacia had ductal in situ Carcinoma … cancer. It was aggressive and fast-moving. Her doctors wanted it out — and quickly. Having no idea of the outcome, Anastacia decided to document her journey — hoping it would help other young women.

She let 20/20 cameras follow her virtually every step of the way, candidly answering questions and talking about her feelings.

"I've never been this afraid. It's just — I'm helpless! At the end of the day no matter what happens, if I do have to take off my breast, if I do have to go through chemo, if I do have to do all the things that go along with this word cancer, I'm gonna be okay. Because, I'm not gonna die. And if I do, I'll die trying," she said.