Note: This copy is for your personal, non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights. ORIGINAL RESEARCH n BREAST IMAGING Radiology: Volume 261: Number 1—October 2011 n radiology.rsna.org 69 Nonmasslike Enhancement at Breast MR Imaging: The Added Value of Mammography and US for Lesion Categorization 1 Isabelle Thomassin-Naggara, MD, PhD Isabelle Trop, MD, MPH Jocelyne Chopier, MD Julie David, MD Lucie Lalonde, MD Emile Darai, MD, PhD Roman Rouzier, MD, PhD Serge Uzan, MD Purpose: To determine the value of adding conventional imaging (mammography and ultrasonography [US]) to nonmass- like enhancement (NMLE) analysis with breast magnetic resonance (MR) imaging for predicting malignancy and for building an interpretation model incorporating all im- aging modalities. Materials and Methods: The institutional ethics committees approved the study and granted a waiver of informed consent. In 115 women (mean age, 48.3 years; range, 21–76 years; 56 malignant, 12 high–risk, and 63 benign lesions), 131 NMLE lesions were analyzed. Two independent readers first classified MR images by using descriptive Breast Imaging Reporting and Data System (BI-RADS) criteria (BI-RADS classification with MR images alone [BI-RADS MR ]) and later repeated this classification, adding information from conventional imaging (BI-RADS classification with combination of MR images and conventional images [BI-RADS MR+Con ]). Lesion diagnosis was established with surgical histopathologic find- ings ( n = 68), percutaneous biopsy results ( n = 25), or 2 years of stability at MR imaging ( n = 38). Receiver operat- ing characteristic curves were built to compare BI-RADS MR with BI-RADS MR+Con . A multivariate interpretation model was constructed and validated in a distinct cohort of 44 women. Results: Values for inter- and intraobserver agreement, respectively, were better for BI-RADS MR+Con ( k = 0.847 and 0.937) than for BI-RADS MR ( k = 0.748 and 0.861). For both readers, the areas under the receiver operating characteristic curve (AUCs) for diagnosis of malignancy were also superior when BI-RADS MR+Con (AUC = 0.91 [reader 1] and 0.93 [reader 2]) was compared with BI-RADS MR (AUC = 0.84 [reader 1] and 0.87 [reader 2]) ( P , .05). An interpreta- tion model combining conventional imaging with MR im- aging criteria showed very good discrimination (AUC = 0.89 [training set] and 0.90 [validating set]). Conclusion: Adding conventional imaging to NMLE lesion character- ization at breast MR imaging improved the diagnostic performance of radiologists, and the interpretation model used offers good accuracy with the potential to optimize the reproducibility of NMLE analysis at MR imaging. q RSNA, 2011 Supplemental material: http://radiology.rsna.org/lookup /suppl/doi:10.1148/radiol.11110190/-/DC1 1 From the Department of Radiology, Centre de Recherche et d’Investigation des Maladies du Sein, Hôtel Dieu, Centre Hospitalo-Universitaire de Montréal, Montréal, Canada (I. Thomassin-Naggara, I. Trop, J.D., L.L.); Department of Radiology (I. Thomassin-Naggara, J.C.) and Department of Gynaecology and Obstetrics (E.D., R.R., S.U.), Hôpital Tenon, Assistance Publique Hôpitaux de Paris, Université Pierre et Marie Curie, Cancer Est, 4 rue de la Chine, 75020 Paris, France. Received January 28, 2011; revision requested March 14; final revision received April 15; accepted May 2; final version accepted May 5. Address correspondence to I.Thomassin-Naggara (e-mail: isabelle.thomassin @tnn.aphp.fr ). q RSNA, 2011