Abnormal amianthoid collagen fibers in meningioma.

Electron microscopic examination of a spinal meningioma demonstrated broad zones with large amianthoid collagen fibers in the tumor. Normal native collagen fibrils were found in small scattered clumps particularly around the blood vessels in the tumor. Such abnormal large collagen fibrils have not been seen previously in meningiomas. The significance of the amianthoid fibers is unknown. The only other unusual feature of the tumor was that it had many pale-staining cells by light microscopy and was classified as a clear cell variant of meningioma.