Hey @crankgranny - thinking of you! The dye test is more than likely called a 'scintigraphy'...it involves injecting radioactive dye into your nipple (or around the tumour) and then you massaging it in for a small while, and then scanning where it drains to.
It took mine about 20 minutes to come up with the node. But everyone is different :) . They will keep checking and keep telling you to massage!
This helps the surgeon to know where your sentinel lymph node is (the major lymph node). It stings a bit, but tbh I was surprised that it wasn't too bad at all. They then identify the node by putting a X on your skin and sending off the scans so your surgeon knows where to go :).
Nikki x