I am 31 and have a huge lump like you. The Dr's thought it was a fibroadeoma but it turns out to be something else. It is benign and I just have fibroidy breasts, lucky me. I am having mine removed. Think the size of a small lemon. Although I am kind of scared, I know that these things can just keep growing. (I personally would like a bra that fits both sides not one ) I made up my mind before I had a core needle biopsy, which was done last friday, that it was time for this thing to go. :) If you have questions you can e-mail me ***@****.
Have they done a core needle biopsy to see if that's what it really is?
Fibroadenomas are benign breast tumors and are often left alone but I can certainly see the wisdom in removing one as large as you describe. This tumor may get even larger and it would really be best to have it removed now. Regards ....