Colloidal iron stains showed that many optic nerve gliomas contain mucoid material. This material is extracellular, as demonstrated especially by electron microscopy of two gliomas. In one glioma it was particularly abundant and it apparently contributed to a sudden increase of proptosis due to rapid enlargement of the tumor. There was no evidence of necrosis or degeneration in these tumors, by light or by electron microscopy, and the accumulation of mucosubstance is not considered to be a degenerative change. The tumor cells were mainly astrocytes. These had certain embryonic ultrastructural features, but did not exhibit malignant alteration.
Anderson DR, Spencer WH. Ultrastructural and Histochemical Observations of Optic Nerve Gliomas. Arch Ophthalmol. 1970;83(3):324-335. doi:10.1001/archopht.1970.00990030326010