Breast magnetic resonance imaging: an essential role in malignant axillary lymphadenopathy of unknown origin.

The aim of this retrospective case series was to assess the role of breast MRI in the investigation of "occult" malignancy, and the associated potential to influence patient management. Between January 2000 and March 2004, 18 patients, who presented with axillary lymphadenopathy, most likely due to "occult" breast cancer, were examined with MRI of the breast. The results showed 12 true positives, four true negatives, and two false positives. This gave an overall sensitivity of 85.7% and an overall accuracy of 86.7%. In those in whom malignancy was identified on MRI and subsequently proven histologically, 78% of these cancers were identified, and localized by preoperative MRI-guided sonography. In addition, 55% of these patients were eligible for conservative surgery. As such, MRI of the breast is highly sensitive for the detection of mammographically and clinically occult breast cancer. The use of MRI enables a preoperative diagnosis to be made in a high percentage of patients and may allow retrospective targeted ultrasound localization. Definitive surgical planning, including the option of breast conservation, is made possible with the result of the MRI examination.