If I heat up my lunch in a less-than-clean microwave, will it contaminate my lunch?

I am at work and the microwave here is gross. No one ever cleans it and I bring a lunch so rarely that I don't feel like cleaning someone else's mess. Today I brought pasta and I need to heat it up but the thought of putting my food in the microwave that's all splattered with food, really grosses me out. If I heat it up in there, with the lid still on but only open a crack, will my food get germs?