ANEURYSMAL BONE CYST

This is a case of 13 yr old boy who came to us with the complaints of pain and swelling just above the shoulder. Plain skiagram was taken and showed large, well –defined expansile lytic lesion with thinned out peripheral cortex at lateral end of clavicle. Few thin septae were also noted within it. The aspirate contained blood. Ultrasound showed a cystic lesion with few echogenic areas within the cystic lesion. On CT, well-defined rounded,epiphysio-metaphyseal expansile, lytic lesion was seen with thinned out cortex was noted at lateral end of clavicle. Sone fluid – fluid levels were also noted. No periosteal reaction was evident.
MRI revealed an isointense, heterogenous lesion on T1WI and hyperintense on T2. Margin of tumour as line of decreased signal intensity is better delineated on T2. Multiple fluid levels are noted. On GRE sequences, few susceptibility artefacts were noted suggestive of blood.
Provisional diagnosis : Aneurysmal bone cyst.