This Sept. 26, 2010, file photo shows Serena Williams arriving at "Macy's Passport Presents Glamorama" event in Los Angeles. People magazine is reporting that Williams has undergone surgery for a pulmonary embolism. Spokeswoman Nicole Chabot tells the magazine that the blood clot in Williams' lungs was discovered last week, and that she had "emergency treatment (Monday) for a hematoma she suffered as a result" of that treatment. Williams is being treated at a Los Angeles hospital. (AP Photo/Chris Pizzello, File)