Radiological features of extraskeletal mesenchymal chondrosarcoma

Objective: To explore CT,MRI findings of extraskeletal mesenchymal chondrosarcoma (EMC). Methods: Imaging information of all 8 cases of EMC verified by pathology were retrospectively analyzed. Results: The location of lesions included lower extremity in 4 cases, forearm in 1 case,trunk in 2 cases and right lung in 1 case. The CT examination was performed in 7 cases, and 5 cases contained different patterns of ring-and-arc, granular, clump or irregular streaky mineralization. Dense calcification was detected in 3 cases,and focal in 2 cases. The nonmineralized component had slightly lower attenuation on CT scans than adjacent muscle. Four cases of peripheral located EMC demonstrated isointense on T₁WI, and mixed signal intensity on T₂WI. For the cases of fine and dense calcification in 2 cases,numbers of dot-like low-intensity signals were detected resembling 'pepper sign'; while for the cases of focal mineralization in 1 case, the low intensity area was located centrally in the high intensity area. Heterogeneous enhancement was found both in the calcified and uncalcified areas. One case of central located tumor exhibited low and high intensity on T₁ and T₂ weighted images, and nodular enhancement was observed. Conclusion: EMC has several characteristic imaging features, including various mineralization pattern, enhancement of calcified area and signal intensity, which might have diagnostic value for this rare tumor. (authors)