Breast Magnetic Resonance Imaging Incidental Findings

Abstract

B reast magnetic resonance imaging (MRI) is now an integral part of breast imaging. It makes valuable contributions in high-risk screening; evaluating the extent of disease, positive surgical margins, and response to neoadjuvant chemotherapy; as well as distinguishing postoperative scar from recurrent disease. [1][2][3][4][5][6] Although the examination is focused on the breast, portions of the neck, thorax, and upper abdomen are also visualized. Just as in computed tomography, the issue of the incidental or unexpected finding must be addressed by the reader.The detection of these findings during diagnosis and surveillance often results in additional testing, economic burden, and anxiety for the patient. Most incidentally detected lesions are benign; however, the reader must consider the potential of these findings to be metastases or additional primary tumors. Approximately 5% to 10% of breast cancers are metastatic at the time of diagnosis. 7 Even with significant advances in breast cancer treatment, up to 70% of node-positive breast cancers will relapse and 20% to 30% of women with stage I and II disease will develop distant metastases, occurring approximately 15 years after radiation therapy. 7,8 Therefore, all detected findings must be carefully considered. A recent study demonstrated the bone, lung, and liver to be the most common anatomical sites of distant metastases in patients with breast cancer, with 21.9% presenting with multisite involvement. 9 The exception to this pattern is the basal-like and triple-negative breast cancers, which have a predilection for visceral and central nervous system metastases and infrequently involve bone. 10 Although lesion detection occurs on potentially any sequence, the 3-dimensional fast spoiled gradient echo axial sequence is reported to be superior to the short tau inversion recovery sequence in incidental finding detection (82.8% vs 76.5%). 11 As in computed tomography, the addition of intravenous contrast enhances lesion detection. Rinaldi et al 11 demonstrated the enhanced 3-dimensional fast spoiled gradient echo axial fat-suppressed axial sequence to have greater sensitivity compared with unenhanced images in detecting metastatic lesions, especially those smaller than 10 mm (98.3% vs 79.3%). These lesions are often on the edge of the field of view and require window manipulation for identification. BREASTDuring the initial extent of disease evaluation, it is not uncommon to discover additional breast lesions. Management of ipsilateral breast findings is directed by their morphology, enhancement characteristics, and proximity to the index tumor. Masses found in the contralateral breast during the extent of disease evaluation raise the issue of an additional primary tumor.Studies have reported an incidence of contralateral synchronous malignancy detected by preoperative MRI to be in the range of 3% to 5 %. 12-14 A contralateral metachronous cancer has been reported to develop in 5% to 10% of patients with breast cancer within a 10-year follow-up. 12 This is especia...