AJR: Breast MRI could be adjunctive tool for inconclusive mammo findings
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Linda Moy, MD, from the department of radiology, breast imaging center at the New York University School of Medicine in New York City, and colleagues sought to evaluate the usefulness of breast MRI in cases in which mammographic or sonographic findings are inconclusive.
The researchers retrospectively reviewed images from 115 breast MRI exams performed from 1999 to 2005 for the indication of problem-solving for inconclusive findings on a mammogram—41.8 percent of the patients were at high risk. They assessed whether sonography or MRI was used as an adjunctive tool and correlated the findings with those in the pathology database.
According to the authors, the equivocal findings most frequently leading to MRI were asymmetry and architectural distortion. No suspicious MRI correlate was found in 87 percent of the cases, which were found stable at follow-up mammography or MRI after a mean of 34 months.
They found that 15 enhancing masses (13 percent) that corresponded to the mammographic abnormality were seen on MRI. All masses identified at MRI were accurately localized for biopsy, and six malignant lesions were identified. Four of six malignant tumors were seen in one mammographic view only; two were seen on second-look ultrasound images.
MRI had a sensitivity of 100 percent and—compared with mammography—had significantly higher specificity (91.7 vs. 80.7 percent), positive predictive value (40 vs. 8.7 percent) and overall accuracy (92.2 vs. 78.3 percent). Also, 15.7 percent of incidental lesions were detected at MRI, and all were subsequently found benign.
Moy and colleagues concluded that strict patient selection criteria should be used because of the high frequency of incidental lesions seen on a breast MRI exam
The researchers said that their data do not support “further evaluation with MRI for all asymmetric findings or for architectural distortion. For most cases of either finding, additional evaluation with mammography and targeted ultrasound is sufficient to make a final BI-RADS assessment. Therefore, only the most vexing cases—subtle mammographic findings in which ultrasound findings are negative or may be inconsistent with the mammographic finding—were further evaluated with MRI.”
The researchers concluded that most of the inconclusive mammograms in their study revealed no corresponding abnormality at breast MRI. Although normal findings at MRI can be more reassuring than normal findings at ultrasound examinations, MRI is not a replacement for sonography.
The authors concluded that they found MRI to be a useful adjunct to conventional imaging in their predominantly high-risk population.