Adamantinomas are rare, low-grade malignant tumors of unknown etiology that usually involve the tibia, fibula, or both. Adamantinoma appears as a central or eccentric, multilocular ("soap bubble" appearance), slightly expansile, sharply or poorly marginated lytic lesion. There are satellite lesions in continuity with the major lesion. Often with reactive bone sclerosis and bowing deformity of the tibia. In the fibula the lesions are more centrally located with sharply demarcated lytic foci with sclerotic margins. The fibular lesions are typically with expansion of the bone contour without bowing deformity.

MRI demonstrates the intraosseous and extraosseous involvement. The differential diagnosis includes osteofibrous dysplasia (OFD), fibrous dysplasia, ABC, chondromyxoid fibroma and chondrosarcoma. A ground-glass appearance with intralesional calcifications suggests fibrous dysplasia whereas the presence of small satellite radiolucent foci is more characteristic of adamantinoma. Surveillance in OFD, with biopsy in case of onset of pain or increased tumor volume.

Case courtesy Dr. Paolo Cucchi Dr Simone Barbieri

Radiographer: TSRM Fabio Imola