Does the peritumoral fat signal on MRI exclude malignancy of soft tissue tumor?

Abstract

MRI is the most sensitive imaging modality in the staging, surgical planning, and following up of malignant soft tissue tumors. However, the ability of MRI to separate benign from malignant lesions is still of limited value for this purpose. We often observe that benign soft tissue tumors are accompanied by a peritumoral fat signal on MRI. The purpose of this study was to determine the value of the peritumoral fat signal in separating benign from malignant soft tissue tumors. We retrospectively reviewed 121 patients with soft tissue tumors (52 men, 69 women; median age 54 years). Two musculoskeletal oncologists reviewed the MRI independently and reported on the presence or absence of a peritumoral fat signal. The sensitivity, specificity, and the positive and negative predictive values of the peritumoral fat signal for the prediction of benignancy of soft tissue tumors were calculated. Peritumoral fat signals were identified in 54 of 64 (84.3 %) benign and 10 of 57 (17.5 %) malignant tumors (p < 0.01). This result had a sensitivity of 84.4 %, specificity of 82.5 %, PPV of 84.4 %, and NPV of 82.5 %. This study permits the conclusion that the presence of peritumoral fat signals is seemingly an exceptional finding in malignant soft tissue tumors. Observation of this peritumoral fat signal should accordingly influence the management of soft tissue tumors.