"I cried," Navratilova, 53, told People magazine about the results of a February biopsy after a routine mammogram revealed a cluster in her left breast.

"It knocked me on my ass, really. I feel so in control of my life and my body, and then this comes, and it's completely out of my hands."

She was diagnosed with a non-invasive form of breast cancer called 'ductal carcinoma in situ', confined to her milk ducts without spreading to the breast tissue.

"It was the best-case scenario you could imagine for detecting breast cancer," Dr. Mindy Nagle, Navratilova’s friend and doctor, added.

The report said Navratilova has already had a lumpectomy and will begin six weeks of radiation therapy in May.

The eighteen-time Grand Slam Singles champion admitted she had not been getting regular check-ups.

"I went four years between mammograms. I let it slide. Everyone gets busy, but don't make excuses," she said.

"I stay in shape and eat right, and it happened to me. Another year and I could have been in big trouble."

Martina Navratilova is one of only three lesbian tennis players to ever reach the top of the world rankings. Till date, she remains to be the only player to have won nine Wimbledon single titles and has spent 331 weeks ranked number one, second only to Steffi Graf.