Nixon, 42, said she had gone for her "completely routine mammogram" in 2006 when she got a call from her gynecologist.
"She says, 'Well I have some, it's not such great news,'" Nixon revealed on Good Morning America Tuesday
Even though she said she felt "scared ... I was very cognizant of it," Nixon said. "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 said she "made a big point" of telling her two children she had the disease. (Nixon is currently dating NYC-based activist Christine Marinoni, following a 2003 split from beau, Danny Mozes.)
"I basically told them they found some cancer in my right breast," Nixon recalled saying. "It's very small and 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," she went on. "This is what grandma went through, and I'm going to be fine."
Nixon — who said she kept her diagnosis private because "I didn't want paparazzi at the hospital" — revealed that her mother had also overcome breast cancer.
"As the daughter of a breast cancer survivor," knowing my personal risk made me more aware and more empowered when I faced my own diagnosis," she said
