Great question. I wish I knew. For me, when diagnosed with mamogram and then a "Wedge" type biopsy, tumor was mucin and 1 1/2 cm. My option was lumpectomy or mastectomy. With a family history I opted for mastectomy -- and it was a good thing because it was not mucin and I had 5 positive nodes. I believe that how they treat depends on how you present. I do know that if the tumor is large, they often try to shrink it before surgery. These ladies here on the board will definitely know the answer to your question.