I have heard that mri is now used for detecting breast cancer. when is it appropriate for women to have a breast mri instead of or in addition to a mammogram?

In addition to: Mri is used in addition to mammography. Just like ultrasound can help to enhance interpretation of a mammogram, MRI can clarify questionable areas.

High-risk,etc.: Mris are more sensitive than mammograms for detecting breast cancer, especially in young women or those with very dense breast tissue; however, they are 20x the cost. Therefore, we reserve mris for women with >20% lifetime risk for breast cancer. They are also very useful for determining if an implant has ruptured, and determining the extent of breast cancer if someone may need mastectomy.

MRI's are also: Associated with "false positives" in the range of 30%, leading to more tests (increased cost), and in some cases ill-advised excess mastectomy. Currently they are being over-used in my community.

High risk: Several years ago the american cancer society published a list of guidelines as to what patient's qualify as high risk sufficient to consider for screening breast mri's. These include patient's with known brca mutations, patient's with prior mantle radiation for lymphoma, patients with a calculated lifetime risk >20%, etc mmgs should continue. For example, microcalcifications show on mmg not mr.

Start with mammogram: Current guidelines recommend the following patients get screening MRI in addition to screening mammogram. 1. Brca mutation 2. First-degree relative of a brca carrier 3. Lifetime risk of breast cancer is 20-25% or greater 4. Radiation to chest between age 10-30 5. Li-fraumeni syndrome, or a first-deg relative 6. Cowden syndrome, or a first-deg relative 7. Bannayan-riley-ruvalcaba syndrome.