Primary:

In women with heterogeneous or dense breast tissue (mammographic types 3 and 4), MBI (Molecular Breast Imaging) will detect more breast cancers and have greater sensitivity in detecting breast cancer than breast tomosynthesis.

Secondary:

1. In women with heterogeneous or dense breast tissue, the specificity of MBI in correctly classifying subjects without breast cancer will be non-inferior to breast tomosynthesis.
2. In women with heterogeneous or dense breast tissue, the area under the receiver operating characteristic (ROC) curve for MBI will be non-inferior or superior to breast tomosynthesis.
3. Combining the use of MBI and breast tomosynthesis will provide performance superior to either technology alone, as manifest by a superior ROC curve area.

Inclusion Criteria:

• Women over 25 years of age with normal or increased risk of breast cancer.
• Women with type 3 or 4 breast density as determined by a breast imaging radiologist on a current unilateral (women with prior mastectomy) or bilateral mammography (within prior 6 weeks).
• No contraindications to breast MBI or breast tomosynthesis.

Exclusion Criteria:

• Women under the age of 25.
• Women who are or may be pregnant.
• Women who are currently lactating or have discontinued breast feeding < 2 months prior to the study.
• Male patients are excluded as subjects.
• Those unable or unwilling to provide informed consent.