Three cases of von Recklinghausen's disease were examined electron-microscopically to obtain characteristics of cellular arrangement and of component cells in the tumors. The tumors consisted of the axons, Schwann cells and fibroblasts, associated with abundant collagenous fibers. Three types of Schwann cell proliferation were found; 1) almost normal structure of the peripheral nerve with axon, 2) Schwann cell wrapping itself in its cytoplasmic process without axon, 3) discrete Schwann cell

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... neither axon nor wrapping cytoplasmic process. Each Schwann cell element was invariably provided with basement membrane and the axons were all unmyelinated. Dense areas like desmosomes were scarcely present between the wrapping cytoplasmic processes. The fibroblasts were closely connected with the Schwann cells, being present in the gap of wrapping Schwann cell or in contact with the outside of wrapping one. The Schwann cell was capable of producing collagenous fibers, although the majority of fibers in the tumors would be derived from the fibroblasts. Also, the Schwann cell was observed to produce the fibers showing the peculiar banded structure at the end of wrapping cytoplasmic process, which was the same area as the collagenous fibers were formed.