Extramammary findings in diagnostic breast magnetic resonance imaging among patients with known breast cancer: incidence and cost analysis

Extramammary findings (EMFs) are common on breast magnetic resonance imaging (MRI). A retrospective review of breast MRIs in breast cancer patients between January 2009 and December 2014 was performed to identify EMF occurrences, resultant evaluation, and added cost. EMFs were noted in 185 (59%) of 316 MRIs. Overall, 201 new EMFs were identified with 178 (89%) benign and 23 (11%) malignant. New malignant findings included 19 metastatic nodes (18 axillary, 1 internal mammary) and 4 primary malignancies (2 thyroid, 2 lung). New malignant nonaxillary EMFs occurred at a rate of 1.6% (5/316). EMFs resulted in 65 patients undergoing 98 imaging studies, 37 procedures, and 10 consultations with a median (range) total charge of $3,491 ($222 to $29,076] and out of pocket cost of $2,206 ($44 to $12,780) per patient. EMFs occurred in more than half of our patients, were usually benign, and frequently led to additional testing and costs.