Ultrastructure of hemangiopericytoma associated with paraneoplastic hypoglycemia.

A recurred and metastasized hemangiopericytoma of menigeal origin caused a terminal hypoglycemia syndrome in a 40 year old man. The disease had been observed over a period of 10 years. The total weight of the tumour metastases was 1800 g. Electron microscopical examination of the tumour cells revealed, in particular, a markedly developed ergastoplasm, prominent Golgi complexes surrounded by many microvesicles, round to ovoid electron dense bodies and fine fibrillar structures. Furthermore, large deposits of basement membrane-resembling material were found in the pericapillary and intercellular spaces. On the basis of the structural characteristics which indicate distinct synthesizing capacity of the cells, an excessive glucose consumption by the tumour is suggested to be an important factor in the pathogenesis of tumour hypoglycemia. The question whether the ultrastructure of the tumour also exhibits secretory processes, which may be related to the release of a presumed inhibitor of hepatic gluconeogenesis and/or glycogenolysis, remains open. Typical granules as in polypeptide hormon secreting cells were not observed. The possibility that the demonstrated electron dense membrane limited bodies represent atypical secretory granules is discussed.