When I had my first mammo at 40 and every year since until this year (I'm 44), I got a "call back". I have dense breast tissue but they could see a "solid nodule" in my left breast. For my first mammo I was terrified because my mom had just started chemo for breast cancer. So every year I got "smashed" and had an ultrasound twice in addition to my annual. But everything turned out alright. The nodule is a lymph node. So I'm perfectly fine. There is a better chance of it being nothing then something but I wish you the best of luck.