Welcome to the best online network anywhere!!! I am 59 and had invasive ductal carcinoma,diagnosed last year.I have finished chemo,and started Tamoxifen yesterday:) I had my sentinel node biopsy at RPAn Sydney,and Imam trying to remember what the gap fee was.The test is expensive,and from memory,I think the gap was somewhere around 200 dollars.Dont hold me to this though!!!Perhaps you could call up the hospital where you are going,and ask about the gap.They are always helpful.This is such an unknown journey,but believe me,with the help and support from this network,teamed with the medical side of it, you couldn't get any better.All the best,and let us know how you go.xoxo Robyn