TY - JOUR TI - Fluid-fluid levels in musculoskeletal tumor imaging AU - Tsukamoto, S. AU - Errani, C. AU - Facchini, F. AU - Papagelopoulos, P. AU - Mavrogenis, A.F. JO - Current Medical Imaging Reviews PY - 2021 VL - 17 TODO - 2 SP - 157-165 PB - Bentham Science Publishers SN - 1573-4056 TODO - 10.2174/1573405616666200806173258 TODO - adenoid cystic carcinoma; angiosarcoma; arthroscopy; autopsy; bone lesion; brain hemorrhage; breast carcinoma; computer assisted tomography; differential diagnosis; epidermoid cyst; erythrocyte sedimentation rate; event free survival; fat necrosis; fibrous dysplasia; fine needle aspiration biopsy; hemangioma; hematoma; histiocytosis; histopathology; human; image analysis; leiomyoma; malignant neoplasm; musculoskeletal disease; myositis; needle biopsy; neurilemoma; neurofibroma; nuclear magnetic resonance imaging; osteomyelitis; osteosarcoma; plasmacytoma; Review; soft tissue tumor; subdural hematoma; thyroid carcinoma; aneurysmal bone cyst; bone tumor; diagnostic imaging; osteosarcoma, Bone Cysts, Aneurysmal; Bone Neoplasms; Humans; Magnetic Resonance Imaging; Musculoskeletal Diseases; Osteosarcoma TODO - Fluid-fluid levels result from the separation of two fluids of differing densities within a cavernous space with the boundary between the two layers running in a horizontal plane at 90 de-grees to the direction of gravity. Magnetic resonance imaging is the most sensitive imaging modali-ty to identify fluid-fluid levels. Although the most common bone lesions containing fluid-fluid levels are aneurysmal bone cyst and telangiectatic osteosarcoma, fluid-fluid levels can be observed in a wide variety of bone and soft tissue lesions. Therefore, fluid-fluid levels cannot be considered diagnostic of any particular type of tumor and the diagnosis should be made on the basis of other clin-ical, radiological and pathological findings. This article summarizes the pathophysiology and imaging characteristics of fluid-fluid levels and discusses the differential diagnosis of tumors with this imaging sign. © 2021 Bentham Science Publishers. ER -