Accuracy of MR Imaging in Diagnosis of Bone Invasion by Soft Tissue Sarcomas: Experience at NCI, Cairo, Egypt

Purpose: To evaluate the Magnetic Resonance (MR) imaging signs and overall accuracy of MR imaging for detection of osseous invasion by soft-tissue sarcomas. Material and Methods: Preoperative MR images of 41 osseous sites in patients diagnosed and treated at the National Cancer Institute (NCI), Cairo University, (2005-2011) for soft tissue sarcomas who underwent surgical bone resection or amputation were assessed retrospectively for signs of osseous invasion, MRI signs assessed included osseous abutment by tumor, cortical destruction, and cortical and medullary signal intensity change on T1- and T2-weighted images. Imaging findings were correlated with histopathological findings. Resuks: Fifteen sites (36.5%) showed osseous invasion histologically. Tumor abutted bone at 26 lesion sites (63.5%). Maximal diameter of osseous abutment and extent of circumferential abutment did not significantly affect osseous invasion. On T1- and T2-weighted images, 13 lesion sites showed cortical signal intensity change (sensitivity, 100%; specificity, 86.7%) and 11 lesion sites showed cortical destruction (sensitivity, 73.3%; specificity, 96.2%). Eleven lesion sites showed decreased medullary T1 signal intensity (sensitivity, 100%; specificity, 96.7%), and 11 lesion sites showed increased medullary T2 signal intensity (sensitivity, 100%; specificity, 96.7%). MR imaging had an overall sensitivity of 86.7%, specificity of 100%, PPV of 100%, and NPV of 93%. Total accuracy was 95% for detection of osseous invasion. Conclusion: Cortical and medullary signal intensity change and cortical destruction on T1- and T2-weighted MR images were sensitive and specific for osseous invasion by soft tissue sarcomas and can be used reliably for preoperative assessment.