Hi Helen. On the advice of my surgeon, I too had chemo first. I had a clip placed in the tumour before starting chemo, in case I reponded really well to chemo, and the tumour disappeared before surgery. It sounds like you're responding really well to the AC. They probably won't know anything definite before surgery.
When you have you surgery, if you'r having a lumpectomy, they will take an area larger than the tumour was on the original scans. This may or may not show scarring from where the tumour was, if you've had a good response. Pathology will pick up any remaining active tumour. The clip won't move from where it was placed. Do you know if you have nodes involved?
Take care, Lyn