An evaluation of enzyme histochemistry in the diagnosis of childhood rhabdomyosarcoma.

Six rhabdomyosarcomas were assessed by means of a battery of enzyme histochemical methods. The reactions were compared with those of a small number of other tumours belonging to the small-cell tumour category. Four of the rhabdomyosarcomas were positive for myophosphorylase and acetylcholinesterase. Myoblasts were strongly reactive for adenosine triphosphatase at alkaline pH and after acid pre-incubation, whereas the small undifferentiated neoplastic cell of the four alveolar rhabdomyosarcomas showed also discernible cytoplasmic reaction, but only after acid pre-incubation. Other tumour categories revealed positive staining for adenosine triphosphatase with acid pre-incubation but the degree of reaction was minimal by comparison. Other enzyme reactions were variable and, generally, did not distinguish between different tumour categories. It is concluded that enzyme histochemistry has a potential role in the diagnostic evaluation of the small cell tumour and should be included in the growing list of special techniques that may assist the pathologist confronted with this problem.