Martina Navratilova has been diagnosed with throat and breast cancer, though a representative described the prognosis as "good".
Navratilova won 18 grand slam singles titles between 1978 and 1990, making her one of the most decorated players of all time.
She underwent successful treatment for breast cancer in 2010, but it has now been confirmed she is battling the illness again.
Navratilova said: "This double whammy is serious but still fixable, and I'm hoping for a favourable outcome.
"It's going to stink for a while but I will fight with all I have got."
Navratilova, 66, was due to travel to Melbourne this month to work on coverage of the Australian Open, a tournament she won three times.
But with her treatment due to start later in January, it has been confirmed she will not be in attendance.
A statement from a representative explained: "The prognosis is good and Martina will start her treatment this month.
"The cancer type is HPV and this particular type responds really well to treatment.
"Martina noticed an enlarged lymph node in her neck during the WTA finals in Fort Worth. When it didn't go down, a biopsy was performed, the results came back as stage one throat cancer.
"At the same time as Martina was undergoing the tests for the throat, a suspicious form was found in her breast, which was subsequently diagnosed as cancer, completely unrelated to the throat cancer.
"Both these cancers are in their early stages with great outcomes.
"Martina won't be covering the Australian Open for Tennis Channel from their studio but hopes to be able to join in from time to time by Zoom."