Hi Julie,
No, I never had the MRI. In fact, I have had no further investigation of the mass. To tell you the truth, it has been there for so long now that I have stopped worrying about it! It has not grown, and I've accepted that it is probably just some sort of benign "fat lump," for lack of a better term. If you've had an ultrasound that didn't detect anything, you're probably going to be just fine. If mine ever starts growing, I'll definitely have it checked out again.
Katherine