Recent incisional biopsy (lumpectomy) question

I had a wire guided incisional biopsy on July3rd.  The BiRad 4 mass was 4.5 cm deep on the right breast at the 11:00 position.  Prior to surgery, discussions with the dr. led me to expect about a 1.5 inch incision and removal of about golfball size specimen (to get the entire mass and clean edges).  
I was very surprised to talk to the dr after the surgery and find that I have a 3.5 inch incision and about a softball size specimen was taken.  

With all the mammograms (about 10 picures), the ultrasound photos and the wire, is it unusual to have this difference from pre-surgery expectations to post-surgery reality?  
If it is benign, why such a large specimen?  

I asked the dr if he found anything of concern; he was encouraging about what he saw but noncommital until the labs are back.  

I am trying to walk on faith but this is an unexpected development after 2 weeks of intensive research and talking to other folks who have had incisional biopsies.

[Cleveland Clinic]

Dear txgrl01:  With an excisional biopsy, the preoperative prediction of tissue removal would be based upon the mammograms and other imaging techniques

[japdip]

Hi, just a comment .... you know 4.5cm is very nearly 2inches ..... I had about the same size incision that you describe and my lump was 2.5cm. Perhaps you just got the wrong impression as to exactly what length the incision would be pre-op. As far as why such a large specimen for a benign lump; until the pathology reports are in there is no way to be sure whether a lump is benign or not. Some measure of tissue must be taken to insure clean margins if the lump is something other than benign.