Hi @MrsMorrisey,
Yes I had one the morning of my surgery back in September - I think it's pretty standard. It involves injection of dye followed by a scan - I believe it's to detect the location of the sentinel lymph node which is the main node the breast drains to.
Then during the surgery they take a biopsy from that node, hopefully get it tested while you're still in surgery, and then if you've given permission, remove the lymph nodes if they're found to be cancerous.
I had the lymph nodes taken under my right arm, but that arm is going pretty well as in no major problems but I still have some numbness and need to do exercises/lymphatic drainage massage.
My worry on the day was about the injections for the lymphoscintiogram (I wasn't worried about anything that happened under general anaesthetic lol) - but my experience was that the injections (I forget how many there were - more than one) were quick and not too painful. I was just worried because they were in the boob area and I thought they might hurt a lot, but they weren't too bad after all.
I hope my simple explanation is correct, I'd run it past the relevant people to make sure, I am a little brain foggy at the moment having just finished chemo but very happy about that too :)
Big hugs and many kind thoughts and prayers for next week!