I Was Diagnosed With Breast Cancer 12/16/2013 And Had An

I was diagnosed with Breast Cancer 12/16/2013 and had an lumpectomy 01/27/2014 then I did the Chemo then Radiation . I just had my first Mammo done last week since the surgery., and the radiologist recommended an ultrasound could it be that it looks abnormal due to the Lumpectomy and that he just need more testing for clarifications or could it be a possibility that the Cancer has came back?