MRI-directed, wire-localized breast excisions: incidence of malignancy and recommendations for pathologic evaluation

Magnetic resonance imaging (MRI) has an evolving role in the evaluation of breast lesions and is currently being used for the screening of high-risk patients (eg, women with a personal or family history of breast cancer), for the evaluation of extent of disease in patients with a current diagnosis of cancer, and for patients with suspicious, but indeterminate, findings by other imaging modalities. If a suspicious lesion detected by MRI is not well visualized by another method, an MRI-directed core biopsy or breast excision may be performed. MRI cannot be used to verify the lesion in the specimen because MRI lesion detection is dependent on uptake of gadolinium after intravenous injection. Accordingly, these breast excisions present unique challenges to pathologists. The purpose of this report is to define the surgical pathology issues involved in processing MRI-localized excisions. Retrospective review of 85 consecutive MRI-directed breast excisions from 77 patients was performed. Malignant lesions were present in 20 (24%) of 85 excisions, including 10 cases of invasive carcinoma (median size, 0.4 cm), 9 cases of ductal carcinoma in situ, and 1 case of lymphoma. Most of the malignancies (85% or 17/20) had no associated gross finding and only 5 (25%) of 20 of these malignancies were associated with a definite finding on the specimen radiograph. This study demonstrates that gross examination and specimen radiography do not identify most of the malignancies in MRI-localized biopsies and, therefore, optimal processing requires complete microscopic examination of these specimens.