The natural history of disappearing bone tumours and tumour-like conditions.

We describe 27 cases of bone tumours or tumour-like lesions where there was spontaneous regression. The follow-up period was 2.8-16.7 years (average, 7.0 years). Fourteen of these cases were no longer visible on plain radiographs. Histological diagnosis included exostosis, eosinophilic granuloma, fibrous dysplasia, fibrous cortical defect, non-ossifying fibroma, osteoid osteoma and bone island. Most cases began to reduce in adolescence or earlier, although sclerotic type lesions showed their regression in older patients. All lesions thought to be eosinophilic granuloma began to regress after periods of less than 3 months, while the duration of the other lesions showed wide variation (1-74 months). As resolution of the lesions took between 2 and 79 months (mean, 25.0 +/- 20.3 months) we consider that the most likely mechanism was recovery of normal skeletal growth control. In exostosis with fracture, alteration of vascular supply may contribute to growth arrest, but not to subsequent remodelling stage. In inflammatory-related lesions such as eosinophilic granuloma, cessation of inflammation may be the mechanism of growth arrest, whilst temporary inflammation may stimulate osteogenic cells engaged in remodeling. In the sclerotic type, growth arrest is a less probable mechanism. Necrosis within the tumour and/or local changes in hormonal control, plus remodelling of the sclerotic area takes longer. Knowledge of the potential for spontaneous resolution may help in management of these tumour and tumour-like lesions of bone.