Jill, you should wait to hear from the doctor - because, in reality, that's your only choice. (S)he's the one who can fill you in on the results of your ultrasound, and what your mammogram might mean. My advice: if (s)he says "It looks like a cyst, it looks benign," ask to have a biopsy to make sure. I've known too many women whose doctors told them "It can't be cancer, it doesn't look like it, doesn't feel like it, you're too young," whatever; and then within a year, they have cancer. Advocate for yourself; it's inmportant, to know one way or the other. Otherwise, you'll just worry; and worry doesn't accomplish anything.  Good luck - PJH