A Diagnostic Consideration of Fluid-Fluid Levels in Bone and Soft Tissue Tumor

To assess the diagnostic significance of the fluid-fluid level (FFL), we reviewed CT and MRI findings of bone and soft tissue tumors exhibiting FFL literature. For the past 10 years, the formation of FFL was reported in 14 of 110 cases of bone and soft tissue tumors. These 14 cases consisted of 8 case of bone tumors (5 of 6 cases of aneurysmal bone cyst, 1 case of chondroblastoma, 1 of 3 cases of intraosseous ganglion, and 1 of 2 cases of fibrous dysplasia) and 6 cases of soft tissue tumors (2 of 21 cases of malignant fibrous histiocytoma, 1 of 14 cases of schwannoma, 1 of 13 cases of hemangioma, 1 of 5 cases of pigmented villonodular synovitis).FFL was most frequently detected by T2-weighted MR images. When FFL is formed by hemorrhagic contents of the cyst, the upper layer showed a higher intensity than the lower layer. Because FFL was observed in various types of bone and soft tissue tumors regardless of their benignancy or malignancy, the diagnostic significance of FFL may be limited. However, FFL was a characteristic feature of aneurysmal bone cyst, because it was observed in 5 of 6 cases of these cysts.