I wouldn't do the biopsy I'd have them remove it and check the tissue after it is gone.
Could be a cancerous tumor and getting it off would be the best thing so why pay for her to have surgery twice? or put her through anesthesia twice?
Goldens are cancer prone but this could be a calcium deposit or arthritic change causing callus growth.
Maybe its a benign cyst.
But if you are going to put her under to get a sample I think you should just take the whole thing and then decide what the next step is depending on what biopsy of the removed tissue shows.
Hope this helps you!
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