I've found limps twice in 3 years, the last time was this Feb this year. I got refered to the hospital where both times I had a mammogram and an ultrasound, all turned out to be fatty tissue, they even found more limps than I could actually feel, I didn't need a biopsy of any kind. So, don't worry just yet, I know it's easier said than done though.
Write down any questions you can think of so you are ready when you get to your appointment, you may be a little nervous and forget them otherwise.
Good luck xx