Large group of small-round-cell tumours of soft tissues and bone represents a 
complex diagnostic problem for the pathologists. Neuronal nature of many tumours 
from this group is proven by means of new methods--immunophenotypic analysis, 
tissue culture, cytogenetics. Peripheral neuroepithelioma, Ewing tumour, 
primitive neuroectodermal tumour (PNET), Askin tumour belong to these neoplasms. 
These tumours anatomically have no connection with the structures of the central 
nervous system or autonomous sympathetic nervous system.