Margins

I recently had a lumpectomy and received a diagnosis of fibromatosis.  I was told that the location of the lump was unusual for a diagnosis of fibromatosis in that it was in the middle of the breast and close to the surface.  After the diagnosis, the doctor said that no further appointments were necessary.  However, after receiving the pathology results on margins, the surgeon now wishes to monitor my situation.  The surgeon told me that although she thought she had obtained large margins, the margins were small and due to the proximity to the surface of the breast wider margins are not possible.  After consulting with a specialist in the area, she wants to monitor me.  I do not fully understand the significance of margins in this situation.  If the diagnosis is fibromatosis and the margins (although small) are clear, why is there still concern?  

[japdip]

With Fibromatosis these are non metastisizing tumors but they can be infiltrative and locally recur. I would think this is the reason for the attention to margins and also the need for close monitoring.   Regards .....