A histochemical and ultrastructural study of a granular cell tumor of the tongue.

Granular cell tumor of the tongue in a 67-year-old woman is reported including details of histochemical, immunohistochemical, and ultrastructural findings.The patient had a chief complaint of a painless nodule that was located slightly right of the midline of the tongue. The nodule, about 4 mm in diameter and having a distinct border, palpated hard-elasticity, and adhered to the muscle layer. Clinically, this tumor was suspected to be benign. The nodule was excised with the surrounding tissue under local anesthesia. The postoperative course is uneventful at present without any evidence of recurrence. The tumor was characterized by acidophilic granules in the cytoplasm. Marked pseudoepitheliomatous hyperplasia of the overlying epithelium was not present. Pathological diagnosis was a granular cell tumor.Histochemically, intracytoplasmic granules were faintly positive in the PAS staining, which was diastase resistant, and negative in the Sudan III and Sudan Black stainings. Immunohistochemically, the tumor cells were moderately positive by reacting with antiserum against S-100 protein, Electron microscopically, granules of various sizes in the cytoplasm of the tumor cell, which was bound by a basement membrane, were revealed, and occasionally myelin figures were noted. According to these results, the tumor cells were suspected to be neurogenic in origin.