Value of MR findings in predicting the nature of the soft tissue lesions: benign, malignant or undetermined lesion?

OBJECTIVE

To evaluate the value of each MRI findings in differentiating the nature of soft tissue lesions.

SUBJECTS AND METHODS

We performed a blind retrospective review of MR imaging in 65 consecutive soft-tissue lesions (cystic lesions in or around the joints, and the soft tissue abnormalities directly related to a known trauma were excluded). Morphology and signal intensity characteristics were analyzed. Each lesion was considered as benign tumor malignant tumor, benign but locally aggressive lesion, and undetermined. The final diagnosis was established pathologically (n = 45), and by the association of other imaging studies, clinical findings and follow-up over 2 yr (n = 20).

RESULTS

Involvement of one compartment was equal in malignant (57.1%) and benign (56.2%) tumors, whereas multicompartmental involvement was most common in non-tumoral lesions (39.1%) (P < 0.05). Well-defined margins were most frequent in benign tumors (189.2%) (P < 0.05). The change from homogeneous to heterogeneous pattern on T1- and T2-weighted sequences as a predictor of malignancy showed a sensitivity of 77.7% and a specificity of 20%. Based on the MRI findings a diagnosis of benign lesion was established with a sensitivity of 60.7% and a specificity of 77.7%; malignant tumor with a sensitivity of 78.5% and a specificity of 96% and benign locally aggressive lesions with 54.5% and 88.1%, respectively. With the addition of the clinical data, an etiologic diagnosis was performed in 78.5% benign tumors, in 85.7% malignant tumors, and in 95.6% benign non-tumoral lesions. Undetermined lesion was diagnosed in eight masses.

CONCLUSION

Soft tissue lesions can be diagnosed with certainty in many benign tumors based on the integrated evaluation of morphology and signal intensity MR findings. The association of MR and clinical data allowed us to identify benign but locally aggressive lesions, mostly related to infection. MR findings are highly specific for malignant tumor, although a histologic diagnosis cannot be performed based only on image analysis. When a mass is undetermined and no criteria for benignity or malignancy can be established, pathologic analysis should be always performed.