Hi Glenlass…the path results from the biopsy will give an indication of the grade i.e. differentiation of the cells, but as the sample taken is quite small, there is margin for error. Biopsy grading compared to tumour removal grading accuracy (according to my research last year) is between 55% and 89% (the higher the grade, the more accurate the pathology). G1 is most like normal cells, G3 most differentiated. After the WLE op the whole tumour is analysed, and the final grade is given. It is highly unusual for the grade to change by more than one grade.
If your nodes look and feel clear, there is still up to a 30% chance that the sentinel node biopsy will show stray cells…again only determined under a microscope. Depending on your hospital, this may be carried out whilst you are ‘under’.
The ‘stage’ is determined after the op, and if you look on this site’s publications, Cancer Research or MacMillan for breast cancer staging this may be helpful. The stage relates to the size of the tumour, whether nodes are affected etc.
When removing the tumours, the surgeon needs to get a ‘clear margin’ i.e. enough ‘normal’ tissue surrounding the tumour to make sure it is all removed. Whether s(he) is able to do this will depend on the size of the tumour, size of your breast and the position of the tumour. Be assured that research shows a WLE + radiotherapy has the same survival stats as a mastectomy. Each of us responds differently to treatment…my WLE/SNB was day surgery and I was advised to take 2 weeks off work, and not to drive for a week. This worked for me. Most important is to do the exercises recommended so that you heal properly and regain strength after the op.
Chemo is usually only recommended if the tumour is G3 or very large in relation to breast and needs to be shrunk, if nodes are affected, if you have vascular invasion (cells found in blood supply to tumour) and some other instances based on individual Onc’s preference for treatment.
Hope your treatment plan gets sorted this week and all your questions answered. There is a publication, I think on this website, which suggests the kinds of questions to ask. Take someone with you to write things down, as it can all be a bit of a blur…however you will get used to the lingo!!
It is a lot to take in, but try (although I know it’s hard) to live in the moment, one step at a time and bring yourself back from the ‘what ifs’…worry is like a rocking chair…moves forwards and backwards but doesn’t actually get you anywhere 
you take care x