petct lit up on l3-l4 vertebra but mri says disc bulge

Siali

hi,i have been diagnosed with IDC LEFT breast and pet ct was done to check for mets. it lit up on my left breast and RIGHT side of l3-l4 vertebra only and no where else.My doc wanted to confirm and a spine mri was done.They said it's a disc bulge. So they want to go ahead with mastectomy left breast. Should i get a second opinion?how do i know it is not bone met for sure?help plz