What are the differentials for a tumor exhibiting fluid-fluid levels?
The differentials include: - Aneurysmal bone cyst - Giant cell tumor - Chondroblastoma - Simple bone cyst - Telangiectatic osteosarcoma.
A large lytic soft tissue mass is seen involving the central medullary cavity of proximal shaft of the ulna. The soft tissue mass is eroding the posterior cortex and extending into the overlying soft tissues. The mass consists of multiple cystic spaces of varying signal intensities separated by thin hypointense septae. The cystic spaces are mostly hyperintense on T1 as well as T2-weighted images indicating internal hemorrhage. Extensive fluid-fluid levels are seen. Relatively narrow zone of transition is seen in the ulna with no marrow edema in the adjoining segments. Mild edema in the surrounding muscles is noted. On post contrast scans, moderate heterogeneous enhancement of the mass is seen, mainly at the periphery and in the septae. Prominent enhancement of the surrounding muscles is also noted.