[Malignant hemangiopericytoma. Apropos of the ultrastructural and histoenzymological analysis of a case].

The histoenzymological and ultrastructural study of a haemangipericytoma with the clinical and histological characteristics of malignancy led to the identification within the tumour, in addition to pericytes and more differentiated cells, fibroblastic or muscular, of younger cells. The latter, arranged in cords undergo multiple appearances of transformation to result in a double maturation, at one and the same time pericytic and angio-endothelial, rarely seen up to the present in haemangipericytomas.