Openly lesbian tennis legend Martina Navratilova celebrates her 54th birthday on Monday.

Navratilova, who dominated the women's tennis circuit for more than a decade, racking up 18 Grand Slam wins and a record 9 women's single titles at Wimbledon, came out gay in 1981. She is among a handful of openly gay sports figures.

In April, she announced that doctors had found a non-invasive cancer during a routine mammogram in January, and that she was undergoing breast cancer treatment. She had a lumpectomy and began six weeks of radiation therapy in May.

“I cried,” Navratilova told Matt Lauer during a Good Morning America interview. “I could not believe it. I thought I was so healthy.”

Navratilova's prognosis is excellent – her type of cancer has a low fatality rate (less than 1%).

Over the summer, just weeks after she finished her breast cancer treatment, Navratilova won an invitational doubles at Wimbledon. Navratilova and tennis partner Jana Novotna went up against the team of Tracy Austin and Kathy Rinaldi.

Happy Birthday to tennis legend Martina Navratilova!