Myoglobin content of granular cell tumor of the tongue. An immunoperoxidase study.

Myoglobin is a protein with a molecular weight of 16,900 daltons that is normally found in adult and fetal striated and cardiac muscle cells. Its synthesis relates to the total ATP requirements of the muscle cell. The histogenesis of the granular cell tumor is controversial, but an origin from striated muscle has been postulated. Seven cases of tongue GCT were evaluated for the presence of myoglobin using the unlabeled antibody (PAP) technique. Normal human striated muscle was used for both positive and negative controls. None of the tumors showed positive staining of the granular cells. Positive controls showed specificity of staining for skeletal muscle. The negative controls did not stain. Granular cell tumors of the tongue do not appear to contain myoglobin. This suggests that either the GCT is not of muscle origin or that, if it is, there may be a metabolic change in the granular cells so that myoglobin is not synthesized. It may be possible that a change in the antigenic determinant has occurred.