Malignant haemangioblastoma (haemangiosarcoma) of the meninges.

The present paper is a report of two cases of malignant haemangioblastoma (haemangiosarcoma) of the meninges. Evidence was found of a tumour made up of vascular proliferation and pleomorphic cells. In case 1 the meningeal tumour had the ultrastructural characteristic of a malignant haemangioendothelioma. In this patient, a spinal tumour found a year later presented the features of a mixed malignant haemangioblastoma. The origin of the tumour in case 2 is the capillary pericyte, the lesion being a malignant haemangiopericytoma. We discuss ultrastucture and properties of the pericyte, its relationship to the cerebral reticulohistiocytic system, and the relationship of malignant haemangiopericytoma with the tumours considered to represent cerebral reticulosis and reticulum cell sarcomas.