Hi Diane,
Although it is unusual (and I want to emphasize that I am not a doctor), it is possible for a recurrence to occur in the remaining tissue after a breast is removed. The only way to know for sure, though is through further testing (and I know how hard the waiting is). Do bear in mind that it is unusual though - and that as someone who is er+, if it is a recurrence, you will have MANY treatment options.
Do keep us posted OK? And take good care-
Laurie