LOS ANGELES: Serena Williams has undergone surgery to remove a blood clot from her lungs, a representative for the tennis star said Wednesday. Nicole Chabot told People magazine that the 29-year-old American underwent an emergency operation at Cedars-Sinai Medical Center in Los Angeles Monday and continues to be monitored by doctors. “Monday Serena Williams underwent emergency treatment at Cedars for a hematoma she suffered as a result of treatment for a more critical situation,” Chabot told the magazine.