Pathology of acoustic nerve Schwannoma in vivo and in vitro.

The ultrastructural pattern of the acoustic nerve Schwannoma was studied on surgically excised tumours and on explants cultured in vitro. The typical neoplastic cell is elongated, spindle-shaped, coated with basement membrane and numerous protruding cellular processes. Cells demonstrating numerous microfilaments are also seen, sometimes intermixed with the typical spindle-shaped cells. Fibroblasts are not uncommon; nor are cells with a round nucleus and rich in organelle cytoplasm, resembling endothelial cells. Numerous collagen fibres and "Luse bodies" are seen in the extracellular space, especially in areas of low cellularity. Round or ovoid cells partially coated with basement membrane are not uncommonly seen in various areas of the neoplasm. In culture, several cells demonstrate fibrillary cytoplasm and long thin cellular processes are frequently seen. Unusual features, such as enwrapping of the cytoplasmic processes forming laminated myelin-like figures are occasionally seen in the surgical specimens as well as in the in vitro cultured explants.