Dear Hanami: The general rule of thumb when a lump is identified is that it should be evaluated by a doctor. That it has been there for over a year and has not grown or changed makes it unlikely to be cancer. Further, cancer is very unlikely in an 18 year old. Nonetheless, it may be a good idea to have a doctor do a check in order to get a baseline exam, help determine what this might be and give you some guidance for the future.