Hi Meredith, sorry to hear that you are going through this too and also coming up with similar attitudes. Currently the best that we have is that a margin of greater than 1cm is recommended and I agree that this is what you need first and foremost. I was told by my surgeon that it was cancer...I had a broderline phyllodes..however many don't call it cancer until it is graded as malignant. All phyllodes tumors do have the potential to become malignant due to their high growth rate, all phyllodes tumors need to be sugically removed with margins to try to prevent reoccurrences. There is very little research on phyllodes - most is retrospective data on treatment after the fact.
If you are after even more information and if you use facebook there are two support groups on there that are worldwide. They are "Phyllodes Support Group" and Phyllodes Tumor, cystosarcoma phyllodes or whatever it is called.
Please ask questions. Hope this helps.
Cheers Katie.