My understanding is that a Sentinel Node Biopsy is used to find out if the cancer has spread into that first 'Sentinel ' node. They inject blue dye into the area and if they find it in the 'first' Sentinel Node, they know it has spread into the Lymph Glands, so they remove those. And if the blue dye doesn't appear in that first Node, you're clear of cancer in those glands. Now, I don't know where we are as regards 'mapping the breast area' because my scar for the Sentinel Node Biopsy is under my arm - not in my breast? The only scar I have on my breast is the surgical incision for my Lumpectomy.