<prompt> Expansile lytic lesion with fluid-fluid levels involing the proximal metaphysis of fibula in an early adolescent female is typical of?Giant cell tumorAneurysmal bone cystHemangiomaFibrous dysplasia  <response>: Ans. b Aneurysmal bone cyst Ref: Bailey 26th533; Grainger Diagnostic radiology 4th ed. 2463Aneurysmal bone cyst is a benign cystic lesion of bone consisting of blood-filled spaces separated by fibrous septa. The lesion is much more aggressive than a simple bone cyst and often presents with pain and swelling. Plain x-rays show commonly aggressive features with eccentric expansion of the cortex and an open physis. MRI. often show multiple fluid levels.Few bone tumors AgeCommon site featuresRadiological SignSpecificAdditional commentsGCT Osteoclastoma20-40 yrs Epiphysis Around knee Lytic Expansile Eccentric Subarticular Soap-bubble appearance Benign bone tumor Conservative surgery like curettage is associated with 40-60 recurrence rate. Up to 4 metastasize to lung.ABC peak age 16 years range 10-30 years; F.M Metaphysis Diatal end of humerus is most common site Purely lytic eccentric radiolucency Expansile ballooning lesion with without Soap-bubble pattern Rapid progression within 6 weeks to 3 months Sclerotic inner portion Tumor respects epiphyseal plate.Fluid-fluid Fluid-blood levels20--30 recurrence rateHEMAN- GIOMA 4th--5th decade; M:F 2:1Vertebra 28 of all skeletal hemangiomas in lower thoracic upper lumbar spine.Vertebra with vertical striations i.e. Corduroy Accordion vertebraPolka-dot appearance on CT Mostly cavernous; In spine Percutaneous Vertebroplasty is a good Rx option.FD Usually early adolescence- MF Usually diaphyseal. Ribs, femur, tibia, jawbones, calvaria, and humerus are most commonly affected, in descending order. Well-defined mixed-density lesionGround-glass appearance or smoky matrix Benign tumor Usually asymptomatic Monostotic form does not evolve into polyostotic form. Polyostotic form accounts for 27 of cases, Monostotic form 70 cases and 3 are seen as a part of McCune-Albright syndrome. In polyostotic form rarely transformation into osteosarcoma malignant fibrous histiocytom may occur. 