AbstractThe past decade has seen significant advances in the treatment of childhood malignancies accompanied by appreciable improvement in survival rates. Treatment programmes have been largely formulated to meet the specific characteristics of individual tumours, as well as being based on the extent of disease presented at diagnosis. In selecting the most appropriate treatment protocol, accurate histological categorization of resected or biopsied tumour is thus of paramount importance. In the paediatric age range in which so many tumours lack differentiation as to present as, or mimic, other small cell tumours, routine methods are often insufficient to resolve problematic histology. A wide range of special techniques is now at hand to assist the pathologist with this problem and this review is an attempt partly to rationalize the application of available methodology. Of considerable importance also is a knowledge of the behavioural characteristics of this group of tumours, their prototypic histology, as well as the range of morphological variability.