[Hemangiopericytoma (author's transl)].

Hemangiopericytoma (HP) is extremely rare in our country. During the last 30 years only two cases were found in the material of our institute. The first case was a tumor of the neck. In spite of little histological evidence of malignancy, local recurrence together with bone metastases occurred four years after removal of the primary tumor. The second case might be a transition of a HP into a hemangioendothelioma. The primary tumor at the lower arm showed the histological pattern of a HP but contained some capillaries with suspicious endothelial proliferations. A nodule in the axilla revealed the pattern of hemangioendothelioma with some areas which resembled a HP. The visceral metastases contained tumor tissue with the typical appearance of hemangioendothelioma. Evaluation of dignity of hemangiopericytomas is extremely difficult. Differentiation of malignant cases of HP from other richly vascularized soft tissue sarcomas and especially from stromal sarcoma of uterus may present problems.