I Had A Mammogram Done And They Found A Mass

I had a mammogram done and they found a mass and they believe its cancer. I'm scheduled for a biopsy and an MRI. The question I wanted to ask you was. I have been pressing down under my breast so forth and noticed a little almost like a little fatty tissue under my breast like on my rib. The top. What could this be? Should I mention this finding? I'm already worried