| Abstract: | The development and ultrastructure of the microvasculature in malignant gliomas The ultrastructural features of the small blood vessels in sixteen gliomas and in their zones of infiltration were compared with normal cerebral capillaries. Extensive new blood vessel formation was seen both in the zones of infiltration and within the main tumour. Immature capillaries in the former had a relatively simple structure with a slit-like lumen containing no blood cells; they resembled capillary buds seen in normal repair tissue and in brain adjacent to a cerebral metastasis. Near areas of necrosis and in pleomorphic regions of gliomas, endothelial cells formed complex, compound immature capillaries with many rudimentary lumina. These appearances are discussed in relation both to the production of tumour angiogenesis factors by gliomas and to the occurrence of gliosarcomas. There was a transition in the structure of the mature capillaries through the zone of tumour infiltration; the vessels gradually changed from normal structure to resemble the capillaries in the main tumour. The endothelial cells became thinner and developed villous processes on the luminal surfaces. Perivascular spaces developed with separation of the glial and capillary basement membranes. Perivascular glial or tumour cell end-feet were seen even in anaplastic gliomas, but in most tumours they formed an incomplete layer around the vessels. The differences between capillary structure in gliomas and in normal brain are discussed in relation to the alteration in the blood-brain barrier observed in gliomas. |
