Granular Cell Tumor of the Thyroid

Granular cell tumors (GCT) can occur in a wide variety of organs, but are rare in the thyroid. To the best of our knowledge, only four cases of thyroid GCT have been reported in the literature. We report a GCT of the thyroid in a girl aged 12 years who presented with a painless neck mass. Thyroid function tests and the serum calcium level were within normal limits. A thyroid ultrasound demonstrated a round hypoechoic mass in the thyroid isthmus. Histologically, the tumor cells demonstrated abundant granular eosinophilic cytoplasm. The tumor cells were positive for S-100 protein and vimentin, and were negative for thyroglobulin, calcitonin, thyroid transcription factor-1, chromogranin A, synaptophysin, and cytokeratin. The patient had no recurrence and remained well at the 10-month postoperative follow-up visit. We reviewed the literature for reports of thyroid GCTs and compared them with reports of extrathyroid GCTs.