"Additional breast cancers found with MRI are sometimes larger and potentially more aggressive than those found on mammography according to a study published online in the journal Radiology. Researchers said that in some cases MRI findings of additional cancers not seen on mammography may necessitate a change in treatment. Breast MRI is the most sensitive technique for the detection of breast cancer with widespread application in the screening of highrisk patients and presurgical planning. In younger women and women with dense breasts MRI is effective in the detection of what are known as multicentric cancers meaning breast cancers involving two or more distinct primary tumors usually in different quadrants of the breast. However there has been some debate about the clinical significance of multicentric cancers found with MRI. Patients with clinically insignificant cancers undergoing potential overtreatment versus patients who may be undertreated is at the heart of the controversy surrounding breast MRI said the studys lead author Chiara Iacconi M.D. from the Breast Unit at USL MassaCarrara in Carrara Italy. To learn more Dr. Iacconi and colleagues reviewed records from  patients with newly diagnosed breast cancer who underwent biopsy after preoperative MRI. Of the  patients  or  percent had additional cancer detected on MRI that was hidden from view on mammography.  In  of those  patients or . percent MRI identified at least one additional cancer in a different quadrant of the breast than the index cancer or the cancer detected by mammography andor breast palpation.  These multicentric cancers were larger than the known index cancer in  of the  patients or . percent. In addition the MRIdetected multicentric cancers were greater than  centimeter in size in  percent of the  patients.  We believe invasive cancer larger than  centimeter is clinically relevant disease Dr. Iacconi said. In general it is accepted that radiation can likely treat invasive cancer less than  centimeter but lesions larger than  centimeter especially invasive carcinomas may not be reliably treated with conservation. The additional MRIdetected multicentric cancers were found mostly in patients with heterogeneously dense or extremely dense breasts. However MRI also detected additional disease in  percent of patients with fatty or scattered fibroglandular tissue.  The results show that multicentric cancer detected on breast MRI after mammography appears to represent a larger tumor burden in approximately a quarter of patients and can result in potential changes to cancer grade and treatment Dr. Iacconi said.   Multicentric Cancer Detected at Breast MR Imaging and Not at Mammography Important or Not Collaborating with Dr. Iacconi on this paper were Lanie Galman M.D. Juntig Zheng M.S. Virgilio Sacchini M.D. Elizabeth J. Sutton M.D. David Dershaw M.D. and Elizabeth A. Morris M.D. Radiology is edited by Herbert Y. Kressel M.D. Harvard Medical School Boston Mass. and owned and published by the Radiological Society of North America Inc. httpradiology.rsna.org  RSNA is an association of more than  radiologists radiation oncologists medical physicists and related scientists promoting excellence in patient care and health care delivery through education research and technologic innovation. The Society is based in Oak Brook Ill. RSNA.org http For patientfriendly information on breast cancer screening visit RadiologyInfo.org http"