Magnetic Resonance Imaging Detects Unsuspected Disease in Patients With Invasive Lobular Cancer M. L. Quan, MD, L. Sclafani, MD, A. S. Heerdt, MD, J. V. Fey, MPH, E. A. Morris, MD, and P. I. Borgen, MD Background: Predicting the extent of disease in the breasts of patients with invasive lobular cancer (ILC) can be difficult because of the limits of physical examination and standard imaging. We determined the utility of magnetic resonance imaging (MRI) in finding otherwise unsuspected cancer in the ipsilateral or contralateral breast of patients with ILC. Methods: Through database review of all breast MRIs performed between January 1, 1999, and December 30, 2002, we identified patients with newly diagnosed ILC who underwent an MRI for extent-of-disease evaluation or contralateral screening. MRI findings separate from the primary tumor were biopsied and correlated with pathology by using MRI-guided biopsy. Results: Sixty-two patients were identified. In all, 59 ipsilateral and 57 contralateral studies were performed. Suspicious lesions separate from the primary tumor were found by MRI in 38 (61%) of 62 patients. Eight patients were excluded from further analysis (seven elected mastectomy without biopsy; one had an unguided excision). Nineteen of 51 patients with an ipsilateral finding underwent MRI-guided biopsy, which revealed cancer in 11, or 22% of those imaged. Twenty of 53 patients with a contralateral finding underwent MRI-guided biopsy, which revealed cancer in 5, or 9% of those imaged. Conclusions: MRI of the breast identifies unsuspected multicentric or contralateral cancer in patients with ILC. These findings support the use of MRI in selected patients with ILC, particularly in the ipsilateral breast. Key Words: Invasive lobular cancer—Magnetic resonance imaging—Image-guided biopsy— Occult cancer. Although invasive lobular cancer (ILC) constitutes only 10% to 14% of all malignancies of the breast, 1,2 its unique presentation, tendency toward multicentricity, 3 and associated higher incidence of synchronous con- tralateral disease 3,4 have generated special interest in its management. Standard screening methods such as mam- mography, ultrasound (U/S), and physical examination have lower sensitivities for detecting lobular cancer com- pared with other invasive breast cancers. The sensitivity of detecting ILC has been reported to be as low as 57% to 76% for mammography 5,6 and 25% to 87% for U/S. 7,8 Physical examination can also be difficult because of vague findings, such as thickening or induration, as op- posed to a discrete nodule, particularly in early disease. Difficulties with all three of these diagnostic methods have been attributed to the growth of tumor cells in single lines throughout the stroma, resulting in subtle physical findings. 9 Magnetic resonance imaging (MRI) relies on physio- logic rather than physical changes and, therefore, has provided new promise for evaluation of the breast and, potentially, for improved detection of ILC. 10 Recent studies have documented that the sensitivity of MRI in detecting malignancy in the breast ranges from 80% to 100%. 11–15 The limitation of MRI, however, is its lower specificity (range, 37%–97%), which results in high Received March 6, 2003; accepted July 6, 2003. From the Breast Service, Department of Surgery (MLQ, LS, ASH, JVF, PIB), and the Breast Imaging Section, Department of Radiology (EAM), Memorial Sloan-Kettering Cancer Center, New York, New York. Address correspondence and reprint requests to: Lisa Sclafani, MD, Breast Service, Memorial Sloan-Kettering Cancer Center, 1275 York Ave., New York, NY 10021; Fax: 631-864-3827; E-mail: sclafanl@mskcc.org. Published by Lippincott Williams & Wilkins © 2003 The Society of Surgical Oncology, Inc. Annals of Surgical Oncology, 10(9):1048–1053 DOI: 10.1245/ASO.2003.03.016 1048