April 15, 2008— -- A year and a half ago, "Sex and the City" co-star Cynthia Nixon was diagnosed with breast cancer, but she kept it to herself.
"I didn't really want to make it public while I was going through it. I didn't want paparazzi at the hospital, that kind of thing," Nixon told "Nightline's" Cynthia McFadden.
It was not Nixon's first brush with the disease. Her mother, Ann, successfully battled breast cancer when Nixon was 12 years old.
"I always sort of thought, 'I'm probably going to get breast cancer. There's a really good chance.'" Nixon said.
After the "Sex and the City" series wrapped, Nixon won a Tony award and was starring in the off-Broadway play "The Prime of Miss Jean Brodie" when she received the news.
"I go for my completely routine mammogram and then I get a call from my gynecologist. And she says, 'Well, I have some -- it's not such great news, but here it is, but it's very small and we're just going to get in there and take it right out, right away, and then you'll probably have radiation,'" Nixon recalled.
"I felt scared. … I thought, 'Oh, I don't want this to be happening.' I was very cognizant of if it's going to happen, this is the best way for it to happen, that it's found so early and we can just get right on it."
Nixon managed to stay sanguine, even scheduling the surgery for a Sunday so that she wouldn't miss even a single performance of her play. She said it was more frightening for those close to her.
"My girlfriend was very scared. … She was the one doing the eating," she said, laughing. "She was in a panic. She was just trying to calm herself down any way she could. And, actually, we made a big point of talking to my kids about it.
"I talked to them together and, basically, I told them, 'You know, they found some breast cancer in my right breast. It's very small. It's very early. I'm going to have an operation. They're going to take it out, and then we're going to have six-and-a-half weeks of radiation every weekday, and this is like what Grandma went through and I'm going to be fine."
Nixon's girlfriend is Christine Marinoni, and four years ago the relationship brought a tidal wave of tabloid attention. They have since become, said Nixon, "just a regular family."
"They love her. They call her Mom," Nixon said. "They call me Mommy. My son is very funny. Sometimes he says Mom, and it's obvious he means both of us or either of us. He just says Mom and whoever answers is fine," Nixon said.
Breast cancer was a subject "Sex and the City" tackled long before Nixon's diagnosis. Nixon said she believes the show handled story of the Samantha character's cancer "beautifully."
Now doing well, Nixon will become the official spokeswoman for the Susan G. Komen for the Cure Foundation for the next year.
"I want them [women] most to hear me saying that the only thing we have to fear is fear itself. So the only thing to really be afraid of is if you don't go get your mammograms, because there's some part of you that doesn't want to know, and that's the thing that's going to trip you up. That's the thing that could have a really bad endgame," Nixon said.