Is your BSN from UT in Austin? I have a BA from there, class of 1990.
Sorry you are facing a recurrence. I have heard where in some cases they cannot locate the primary tumor. I would think that they would want to do a node dissection to see how many are cancerous and to remove it surgically. From there, they can at least determine for sure if it is breast cancer as opposed to any other kind (perhaps they have already done so?). At least if they know for sure that it's breast cancer, they can treat it as such.
Keep us posted along the way...