Histogenesis of endocardial tumors in rats

10 endocardial tumours (two tumours induced by N-nitrosoethylurea and eight spontaneous) of BD VI rats were examined for protein S-100 using specific antiserum in an immunoperoxidase reaction. The presence of protein S-100 in tumour cells is demonstrated in all cases and is considered as a proof of Schwann cell origin of these tumours.