What is the difference between an ultrasound of breast and a mammogram?

Sonar vs Xray: Breast ultrasound use sound waves (i.e. Sonar) and are used to determine if a lump is solid, (usually require biopsy) or a cyst (a fluid containing lesion, usually not requiring biopsy). Mammograms also detect tumors in the breast and have the advantage of detecting tiny calcification deposits that my be due to cancer. Both tests work together to find breast cancer. No test replaces the other.

Mammo vs ultrasound: A mammogram is a low dose X-ray of the breasts. An ultrasound utilizes sound waves to generate images. Mammo is currently the standard of care for screening, ultrasound has an adjunct or problem solving role.