I got a BI-RADS 3, probably benign, reading on an MRI 4 months ago. I was told to wait 6 months and take another MRI to find out of the spot changes. What I've read on pubmed.gov is that this could go on for 3 years, that is, having an MRI every 6 months. I asked why not do an ultrasound-guided fine needle biopsy, and she said that a 0.5 cm spot can't be seen by ultrasound and therefore a biopsy wouldn't work. I'm not sure I believe this as I think she's maybe been wrong about other things. I hate knowing that every MRI leaves gadolinium behind in the bones, brain and other organs, but I guess I'll have to go through with it.