Ultrastructure of cerebellar capillary hemangioblastoma. III. Crystalloid bodies in endothelial cells.

The endothelial cells of three cases of cerebellar capillary hemangioblastoma were studied by means of electron microscopy. Crystalloid bodies, not previously described in the vessels of the central nervous system (CNS), were found in 5%-10% of the endothelial cells, more often in the capillaries with small irregular lumens. They were not observed in the pericytes or stromal cells. They were round to polygonal, 0.5-1.0 micron in size and composed of substructural units of parallel thick and thin electron-dense lines with a periodicity of 180-220 A. They coexisted occasionally with Weibel-Palade bodies but shared no structural correlation with them. The nature and significance of these crystalloid bodies are as yet unknown. Their close association with pinocytic vesicles suggests that the substructural crystalline might be the result of reconstruction of absorbed material from either the vascular lumen or the interstitium. Their subsequent development, associated with lysosomal activity, into intracytoplasmic dense bodies is postulated. Since crystalloid bodies were found only in endothelial cells, particularly those active in proliferation, they may play a pathophysiologic role in relation to angiogenesis.