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Primary Optic Nerve Meningiomas in F344 Rats

Primary optic nerve tumors are very rare in the rat." In this paper, we describe light and electron microscopic and immunohistochemical features ofa spontaneous primary optic nerve meningioma and a chemically induced meningioma in F344 rats. To our knowledge, this is the first report of such tumors in F344 rats. Case No. I, a 105-week-old male rat, had the only primary meningioma of the optic nerve identified in the National Toxicology Program's database program that described results from approximately 60,000 male and 60,000 female F344 rats. This rat was in the high-dose group of a 2-year inhalation study of 2,2' -epoxybutane. Because there were no