Spontaneous osteosarcoma of the meninges in an albino rat.

A search of the rat tumor literature revealed no papers on naturally occurring primary osteosarcoma of meninges. In humans, this tumor, arising primarily from the meninges, is unusual; only two cases have been reported. We report on a spontaneously occurring osteosarcoma arising from meninges in a 2-year-old female albino rat. The diagnosis was made on the basis of gross, microscopic, and ultrastructural findings. The diagnosis of this neoplasm is supported by the fact that a primitive mesenchymal cell in the meninges is capable of giving rise to a wide variety of neoplasms.