What Causes Swelling On Labia Majora?

Hi, My name is Vanessa, I'm 20 years old. I have this unusual swelling on my labia majora. Its under the skin and round, just smaller than golf ball sized. Its not painful, just obnoxious From the reading I've done online its possibly cancer? I have an appointment to get it checked out next week, but I'm losing sleep over this and wondering if I can get any answers before that.