The role of contrast enhanced MRI in the diagnosis of non-mass image-forming lesions on breast ultrasonography.

BACKGROUND: Although non-mass lesions on breast ultrasonography have become relatively common, they remain very difficult to diagnose. The purpose of this study was to evaluate the usefulness of contrast enhanced magnetic resonance imaging (MRI) in managing non-mass lesions. METHODS: A total of 82 cases of non-mass lesions visible on breast ultrasonography who were subjected to contrast enhanced MRI (CE-MRI) were available for assessment. These lesions were evaluated in terms of the association between the enhancement pattern on contrast enhanced MRI and the pathological or cytological diagnosis. RESULTS: Thirty-three of 82 (40.2%) non-mass image-forming lesions were seen as enhanced lesions on CE-MRI, of which 32 revealed non-masslike enhancements. Of the 19 breast cancers detected as non-mass image-forming lesions, 18 (94.7%) had an enhancement pattern not suggestive of a mass, so breast cancers comprised 56.3 % (18/32) of the lesions. Most of the breast cancers tended to emerge in a setting of duct dilatation with internal echoes (45.5%; 5/11) or low echo areas with indistinct margins (32.4%; 11/34). Morphologically, segmental (57.9%; 11/19) and regional (21.1%; 4/19) enhancements were common patterns of breast cancer which showed up as non-mass image-forming lesions. On the other hand, 49 of 82 (59.8%) non-mass image-forming lesions were not enhanced and 28 of 49 cases underwent pathological examination. Only one case was breast cancer with category 5 microcalcifications and although about half of the remaining 21 cases were followed for at least 12 months, no breast cancers were found. CONCLUSION: Contrast enhanced MRI was useful for detecting breast cancer in cases of non-mass image-forming lesions. On the other hand, except for cases in which mammography was suspicious for malignancy, lesions showing no enhanced areas may be safely followed, because the possibility of breast cancer is minute.