NEW YORK -- Tennis great Martina Navratilova has been diagnosed with a noninvasive form of breast cancer and her prognosis is considered excellent.
Navratilova said in a phone interview Wednesday that a routine mammogram in January found a lump, and a biopsy the following month determined it was ductal carcinoma in situ, or DCIS. The nine-time Wimbledon women's singles champion had a lumpectomy in March and will start six weeks of radiation therapy next month.
"It was such a shock for me," Navratilova said. "It was my 9/11."
In an appearance Wednesday on ABC's "Good Morning America," Navratilova told interviewer Robin Roberts, herself a breast cancer survivor, "It is just in that one breast. I'm OK and I'll make a full recovery."
According to the National Institutes of Health, more than 50,000 women each year are diagnosed with DCIS, in which abnormal cells haven't left the milk duct to penetrate breast tissue. It's removed because it is a risk factor for developing invasive cancer. Only about 2 percent of DCIS patients die of breast cancer in the next 10 years.
People magazine's Web site first reported Navratilova's diagnosis.
Navratilova said she initially wanted to keep her diagnosis quiet but decided she could help others by going public. She will do a Web chat Thursday in her role as the AARP's Health and Fitness Ambassador, when she hopes not only to teach participants but also to learn from them.
Navratilova plans to work as a commentator for the Tennis Channel during the French Open while undergoing radiation therapy in Paris, and she wants to hear from others whether she'll have the energy to do that.
Navratilova said on "GMA" that she is fine physically but struggles emotionally at times, particularly when discussing her diagnosis.
"I'm this healthy person, I've been healthy all my life, and all of a sudden I have cancer. Are you kidding me?" she said.
One of the most accomplished tennis players in history and an outspoken voice for social causes, Navratilova won 59 Grand Slam titles overall, including 18 in singles, 31 in doubles and 10 in mixed doubles. The last was a mixed doubles championship with Bob Bryan at the 2006 U.S. Open, a month shy of Navratilova's 50th birthday.
She originally retired in 1994, with a record 167 singles titles and having spent 331 weeks ranked No. 1. She returned to the tour as a doubles player in 2000 and couldn't resist dabbling in singles, including a first-round victory at Wimbledon in 2004.
Information from The Associated Press was used in this report.