New boob abnormality

So I went and saw the surgeon on Monday and was relieved to find out that it was localised to the breast only and they booked me for a mastectomy for Friday. They said I would have some minor chemo type drugs and I thought this is fantastic! Best news! Then today I went to see the oncologist who started out saying that I could have Docetaxol treatment followed by herceptin and pertuzumab 3 weekly for the rest of my days or I could just have TDMI for a year and hope it doesn't come back. She was very keen on the TDMI for a year until she examined me and then she said "that's really large, isn't it!" She then backtracked and said she thought it was too big to get clear margins in a mastectomy and that I should start chemo asap. She said I could have Taxol instead of Docetaxol for 18 weeks and said she felt it had the same efficacy and I tolerated Taxol well last time. I'm starting tomorrow. I'm a bit freaked out as she said it is large and growing rapidly. I guess all I can do is hope it responds to the Taxol well again and we get a good outcome but it feels a bit gloomier now than it did with the surgeon.