Tennis icon Martina Navratilova opened up to CNN about her battle
with
breast cancer and her comeback to win the doubles competition at the
French Open less than four months after learning of the diagnosis.

"I heard on February 24, which is kind of like my 9/11. You don't forget the day when your life is completely changed forever," she said in the documentary Martina: My Toughest Opponent, premiering Sunday in the United States. "Although I did not hear the word 'cancer,' your biopsies [are] positive. I am like 'positive is usually good, wait a minute, that is not good, what does it mean?'"

Navritalova was diagnosed with the most common type of noninvasive breast cancer, ductal carcinoma in situ, or DCIS. She had undergone a lumpectomy weeks after being diagnosed, followed by several weeks of radiation.

Martina: My Toughest Opponent follows the Czech-born athlete from her diagnosis through radiation therapy and then back to the court winning the doubles competition at the French Open and Wimbledon this summer with Jana Novotna.  She said she is sharing her story with others to encourage more women to get regular mammograms, unlike she did.

Watch the full documentary on CNN.com