[Pituitary hemangiopericytoma].

Information on the first observation of the hypophyseal hemangiopericytoma having the clinical symptoms of hypophyseal adenoma is presented. It is noted that such tumours can be mistakingly diagnosed as adenomas. Therefore on the basis of light microscopical, histochemical and electronmicroscopical data a tactical diagnostical algorithm is worked out and proposed that facilitates the distinguishing of hemangiopericytoma among other tumours of the hypophysis anterior lobe.