breast mri showed cysts on liver, could this be mets?

hi folks,
I had a breast mri for a lump that i have on my lumpectomy scar, i still do not know what the lump is and the bcn said the scan has shown cysts on my liver, i have to get an ultrasound , i am not sure why they want to do an ultrasound as i thought mri was more sensitive, could this be mets? according to the nurse these are common? anyone know about this. Also when i go to see the doctor should i ask for a biopsy to see what the lump is?
as ever thanks xxxxxxxxxxxxx