Billie Jean King has reacted to Martina Navratilova recently announcing that she has been declared cancer-free by the doctors involved in her care.Navratilova who had been diagnosed with Stage 1 throat and breast cancer earlier this year announced on social media that she had gotten the 'all-clear' following a full day of tests at the cancer institute where she was being treated.Referring to the news as 'terrific', King stressed that her compatriot was 'always a fighter'. The 66-year-old had been diagnosed with an early form of breast cancer back in 2010 as well but came through unscathed following a complete recovery."Terrific news. Always a fighter," Billie Jean King wrote on Twitter.Billie Jean King@BillieJeanKingTerrific news. Always a fighter. wtatennis.com/news/3546068/n…4099225Terrific news. Always a fighter. wtatennis.com/news/3546068/n…Billie Jean King is the latest among a host of celebrities from within and outside of the tennis fraternity to have expressed their joy after Martina Navratilova's social outlined her medical status.The 18-time Grand Slam champion had stunned the sporting world with a tweet in early January where she chose to refer to her diagnoses as a 'double whammy'.Billie Jean King had earlier come out on social media to express her happiness when Navratilova broke the news that her cancer was in remission during a talk show hosted by Piers Morgan."Such wonderful news from my dear friend, Martina. We are so happy for you," she had tweeted in March.Despite sharing an on-court rivalry with Martina Navratilova during their playing days, Billie Jean King has confirmed the two tennis legends also share a lasting friendship.Epic rivalry that grew into a lasting friendship - Martina Navratilova and Billie Jean KingNavratilova in action at the 2010 Wimbledon ChampionshipsTennis fans the world over were in for a treat when Billie Jean King shared a video of herself hitting a few balls with longtime friend and rival Martina Navratilova last year.While the Czech-American was seen sporting an all-white tennis outfit, King who was dressed formally, was seen on the opposite court as cheers rang out from onlookers as the rare spectacle unfolded at Indian Wells."What a thrill and a privilege to hit a few balls with @Martina. The years have passed, but the friendship and memories remain," Billie Jean King wrote on Twitter.Billie Jean King@BillieJeanKingWhat a thrill and a privilege to hit a few balls with @Martina. The years have passed, but the friendship and memories remain.8898457What a thrill and a privilege to hit a few balls with @Martina. The years have passed, but the friendship and memories remain. https://t.co/UJp7TD4DSZNavratilova and Billie Jean King faced each other a total of 14 times with the Czech American winning the last encounter between the two, which was played in 1981. King trails 6-8 as far as the overall head-to-head stats are concerned after winning the first four matches between the two on the trot.Both Billie Jean King and Martina Navratilova have won a total of 20 career titles at Wimbledon, including triumphs in singles, women's doubles, and mixed doubles events. The two tennis greats have also won 12 Grand Slam singles titles each.