[Extramedullary Ewing's sarcoma].
The authors refer to six observations of periostal Ewing's sarcoma and describe its X-ray symptomatology. It differs considerably from the commonly known picture of centrally, intramedullar-originated Ewing sarcomas and tumours, diagnosed at considerable advanced stage. The possibility of periosteal origin of Ewing's sarcoma must be considered in differential diagnosis of periostoses and the patients must be examined in a complex way, particularly by computer tomography (and in the future also by MR tomography) in order to demonstrate that the medullar space of the bone is not affected by the tumour. This enables a more considerate resection during the operation. Histological verification of the nature of the tumour and excluding presence of the tumour cells in bone marrow dissection material is necessary. It may be expected that prognosis of this form of Ewing's sarcoma while treated in a modern combined way is more favourable than in the central forms.