Carla Suarez Navarro has been diagnosed with Hodgkin lymphoma and will undergo six months of chemotherapy.
Former world number six Suarez Navarro last week withdrew from the US Open due to health reasons.
The 31-year-old Spaniard announced last December that the 2020 season would be her last on the WTA Tour.
In a video posted on her official Twitter account on Tuesday, Suarez Navarro said: "Hi everyone, just wanted to let you know that a few days ago I have been diagnosed with lymphoma. It's Hodgkin lymphoma. I'll need to go through six months of chemotherapy.
"I'm fine and calm at the moment, willing to face whatever comes."
The accompanying tweet read: "I have to face a complicated reality. It is time to accept it and try to move forward relying on medical advice. Always with positivity in the face of adversity.
"Patience and self-belief guided me through my career. Not the easiest rival to deal with. I'll need my true best."