Absence of myelin basic protein in granular cell tumors.

Thirty-one granular cell tumors were studied for the presence of myelin basic protein (MBP) using a monoclonal antibody with a characterized specificity and an immunoperoxidase technique. The tumors studied were from all areas of the body, from both sexes, and from nine decades of age. All the tumors stained negatively for MBP. One brief report using a monoclonal antibody had noted positive staining for MBP in granular cell tumors. A more recent study using polyclonal antibodies found negative staining for MBP in Schwann cell neoplasms including granular cell tumors. This study, using an immunohistochemical technique, demonstrated the absence of an MBP marker in granular cell tumors of diverse location despite the fact that granular cell tumors are widely held to be of Schwann cell origin.