Reoccurring Neuroma

Hi,
My beloved 12yrs female sheltie/mix has had a neuroma removed from the same spot 2 times in the past 3yrs. The first time it almost sprung up overnight.It was removed within a week of it showing.It was a very low level malignancy.
The 2nd time it was much slower. The doc wanted to watch it for a little while but it seemed to start growing rapidly agin and was removed. Agin the same exact place ,the exact same thing and the same level of malignancy. She is otherwise very healthy and in great shape for her age. All her blood tests show everythings perfectly normal.
Has anybody else delt with these?
Any info would be great....
Thanks , Theresa