The purpose of this study is to compare conventional breast imaging and diagnostic work-up (2 dimensional imaging) to digital breast tomosynthesis (3 dimensional imaging) in the appearance of non-calcified breast masses. It is thought that non-calcified breast masses will be better visualized with the new 3D technology.

Inclusion Criteria:

• Female
• Any race or ethnicity
• At least 35 years old
• Prior screening or full diagnostic mammogram at Barnes Jewish Breast Health Center

Exclusion Criteria:

• Unable or unwilling to undergo informed consent
• Subjects who have breast implants
• Subjects who are unable or unwilling to tolerate compression
• Subjects who are pregnant or who think they may be pregnant
• Subjects who are currently lactating
• Men
• Women less than 35 years old
• Women greater than 80 years old
• Subjects whose breasts are larger than the tomosynthesis detector