My rat has a bubble near neck to shoulder

Question
My rat has a bubble from her neck close to her shoulder and a bit underneath she has had it for a while it doesn't seem to hurt her although me and my girlfriend are unsure. What do you think it could be and how can we help her?

Answer
Is it covered in fur or is it on top of her fur? IS there a scab on it?  It could be either an abscess or a tumor, which can be removed easily.  If I knew if it was an abscess I can help you get it to open and drain easily but if it is a tumor, you can help her by taking her to the Vets and if you dont have one please let me know and i can help find one in your area that takes care of rats.