Hi apandy....you sound pretty devastated on all counts. I can't comment on the altruistic kidney donation situation, except to say what a special act to have planned; albeit probably not going to happen now. On a lesser note since chemo I have had to stop donating blood, and yet to check out (more than my brain can handle at the mo!!!) about organ donation having had bc. I guess there are stringent rules in place to protect patients in this litigious society we have become!
On the diagnosis front, the path results from biopsy can give a reasonably accurate indication of grade (although that could change either way once the lump has been removed) and the ultrasound/palpation of the lump again can give a reasonable idea of size, but the actual size cannot be determined with 100% accuracy until after surgery and the offending lump has been removed. If ultrasound or physical exam did not indicate any spread to lymph nodes, there is again a chance teeny cells (only visible under a microscope) may be present.....depending on your hospital, they may remove the sentinel node (the first one the breast drains to) whilst our are 'under' and check it. Action will depend on results....either stitch you back up or do a partial/full node clearance. Your surgeon will explain all this to you next week, but it will probably be a blur! Try and take someone with you and some ready-prepared questions. I believe BCC has a useful checkist?
Be reassured that your diagnosis is unique to you, as will be your treatment...WLE (lumpectomy) + radiotherapy has as good survival rates as a mastectomy. Chemo again is individual and varies between hospitals, but a rule of thumb is if nodes are affected, the lump is grade 3 or HER2+ (not exhuastive!!!) and if your team feel there will be any longer term benefit.
Most important now is to enjoy your holiday, try to focus on the present, not the 'what ifs' (easier said than done!). You will get through this with the love and support of those close to you. You take care x