Unifocal Langerhans' cell histiocytosis (eosinophilic granuloma) resembling Ewing's sarcoma

In a 9 year old boy, a destructive lesion in the diaphysis of the right femur was wrongly diagnosed as a Ewing's sarcoma on the basis of the radiologic findings and fine needle aspiration cytology report. The clinical and radiologic picture was suggestive of Ewing's sarcoma, but an open biopsy of the lesion revealed a histopathological pathological picture of eosinophilic granuloma. A brief review of the literature is given, together with discussion on the differential diagnosis of a mid shaft femoral lesion in young patients.