What's the difference between mammogram and ultrasound for breast cancer detection?

Complementary. A mammogram is an excellent screening test, designed to find cancers before they are palpable. An ultrasound is best utilized for determining the severity of what was seen on mammography. Using the info from both studies, we can then decide if biopsy is necessary. Ultrasound is also a tool to supplement physical exams--it's like a stethoscope for breast surgeons.
Mammo/ultrasound. Across the board, screening mammography detects approx. 3-5 cancers per 1000 patients. Some studies show that screening ultrasound can detect an additional 2-3 cancers per 1000,and is particularly particularly useful in dense breasts, where the sensitivity of mammo for detecting cancers drops from 80% overall to less than 50%.. They are complementary tests,and the role of US is currently evolvin.
What they see. Mammograms use x-rays to evaluate the breast. They look for abnormal deposits of calcium that can be a sign of breast cancer. Ultrasound is used for lumps for which the significance is uncertain. Ultrasound can tell the difference between fluid filled cysts (that are benign) and solid masses that should be biopsied. This is especially useful in younger women where cysts are common.