My Lilly Mae is a rescue that came to me 2 yrs ago. When we got her , her whole tummy from her pelvic to her armpits were covered in tumors. She only needed 1 mastectomy in the same breast as your babies lump is and the rest of the tumors were removed individually she was spayed and had most of her teeth pulled, surgery took about 3 hrs. She was 10 yrs old at that time and she recovered quickly & has been doing very good since. I pray your baby will deal as good as mine did and she will be good as new in no time. You may have said & I missed it but I hope she will be spayed at the time of her mastectomy. Sending good thoughts your way