Immunohistochemical localization of S-100 protein and peripheral nerve myelin proteins (P2 protein, P0 protein) in granular cell tumors.

The presence and distribution of nervous-system-specific protein (S-100 protein), peripheral nerve myelin proteins (P2 protein and P0 protein) that have not been given any attention in the field of tumor pathology, and striated muscle-related proteins (myoglobin and myosin) were studied in 18 cases of granular cell tumor by the peroxidase-antiperoxidase method. The granular cells of all cases were negatively stained with anti-striated-muscle-related protein antiserums. On the other hand, they were positively stained with anti-S-100 protein, P2 protein, and P0 protein antiserums. The distribution of P2 protein and P0 protein corresponded with that of characteristic PAS-positive granules on serial sections. Angular bodies in the interstitial cells were also positively stained with anti-P2 protein antiserum and anti-P0 protein antiserum. These results further support the hypothesis that the granular cell tumor is derived from Schwann cells and also suggest that myelin proteins are major core proteins of the characteristic granules and angular bodies of interstitial cells. The biologic significance of these results in relation to myelinogenesis is also discussed.