Cancer testing....with an ULTRASOUND?

So a girl in my youth group (used to be a friend, not anymore because she was way too overbearing and getting on my nerves) thinks she has cancer. She went for an ultrasound today, and then told the youth group about it, and how they're "Studying the ultrasound". I'm just wondering if they use an ultrasound as a diagnostic tool in diagnosing cancer...and I wasn't quite sure how they could study an ultrasound unless it was recorded, like an x-ray, but on tape? I thought you had to have a mammogram to confirm cancer, since I thought an ultrasound was mostly to diagnose larger things than a lump in the ? Anyway...what do you think? Is she just saying it for attention, or is this a valid way to diagnose cancer?