Background: We previously demonstrated that superparamagnetic iron oxide (SPIO)-enhanced MR imaging is\r\npromising for the detection of metastases in sentinel nodes localized by CT-lymphography in patients with breast\r\ncancer. The purpose of this study was to determine the predictive criteria of the size of nodal metastases with\r\nSPIO-enhanced MR imaging in breast cancer, with histopathologic findings as reference standard.\r\nMethods: This study included 150 patients with breast cancer. The patterns of SPIO uptake for positive sentinel\r\nnodes were classified into three; uniform high-signal intensity, partial high-signal intensity involving =50% of the\r\nnode, and partial high-signal intensity involving <50% of the node. Imaging results were correlated with\r\nhistopathologic findings.\r\nResults: Thirty-three pathologically positive sentinel nodes from 30 patients were evaluated. High-signal\r\nintensity patterns that were uniform or involved =50% of the node were observed in 23 nodes that contained\r\nmacro-metastases and no node that contained micro-metastases, while high-signal intensity patterns involving\r\n<50% of the node were observed in 2 nodes that contained macro-metastases and 8 nodes that contained\r\nmicro-metastases. When the area of high-signal intensity was compared with the pathological size of the\r\nmetastases, a pathologic >2 mm sentinel node metastases correlated with the area of high-signal intensity,\r\nhowever, a pathologic =2 mm sentinel node metastases did not.\r\nConclusions: High-signal intensity patterns that are uniform or involve =50% of the node are features of nodes\r\nwith macro-metastases. The area of high-signal intensity correlated with the pathological size of metastases for\r\nnodes with metastases >2 mm in this series.
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