Granular cell tumor arising in myelinated peripheral nerves: light and electron microscopy and immunoperoxidase study

The histologic, immunohistochemical and ultrastructural characteristics of two granular cell tumors arising from the right recurrent laryngeal and left facial nerves are described. S-100 protein was detected both in the nuclei and cytoplasm of the granular cells using the peroxidase-anti-peroxidase method. The ultrastructural findings in both cases support a Schwann cell derivation of the granular cells. It is suggested that the granularity of cells of granular cell tumor may represent a lysosomal disorder affecting most frequently neoplastic and nonneoplastic Schwann cells and occasionally other cells.