I highly recommend the following article on circulating tumor cells (and Isolated tumor cells in bone marrow):
http://breast-cancer-research.com.la...ontent/8/5/110
It seems even a single isolated tumor cell in your bone marrow or a single circulating tumor cell in your blood could be used to find your 70 gene profile or entire multigene array ie, the exact genetic content of your tumor to help customize your treatment ie, not all her2 tumors are alike and not all respond to herceptin.