Soap-bubble appearance on X-ray is characteristic of

OSTEOCLASTOMA (GIANT CELL TUMOUR) Giant cell tumour (GCT) is a common bone tumour with variable growth potential. Characteristic radiological features of this tumour: A solitary may be loculated, lytic lesion. Eccentric location, often subchondral Expansion of the overlying coex (expansile lesion). 'Soap-bubble' appearance - the tumour is homogeneously lytic with trabeculae of the remnants of bone traversing it, giving rise to a loculated appearance. No calcification within the tumour. None or minimal reactive sclerosis around the tumour. Coex may be thinned out, or perforated at places. Tumour usually does not enter the adjacent joint. Reference: Maheshwari; Essential Ohopaedics; Page no: 238