<prompt> An 8-year-old child presented with pain at shoulder and arm. A X-ray reveals a uniform well-defined lucent lesion at the metaphysis. Most likely diagnosis is?AIIMS 2016Simple bone cystAneurysmal bone cystGiant cell tumourOsteoid osteoma  <response>: Ans. A Simple bone cystLucent geographic lesion seen in humeral metaphysis in a child is most commonly a simple bone cyst. Trapdoor signQFallen fragment signQHinged fragment signQ may be seen. 