C

MRI can demonstrate the characteristic multiple fluid–fluid levels and thin peripheral shell seen in an aneurysmal bone cyst, which is suggested by a blood-filled aspirate and expansile lytic lesion without periosteal reaction; these MRI findings are considered diagnostic and distinguish it from metabolic or metastatic causes [Beltran, 1986, PMID 3945739; Sandomenico, 1996, PMID 9036439].