Granular cell tumor of the thyroid: Clinical and pathological characteristics of a rare case in a 14-year-old girl.

Granular cell tumors (GCTs) are soft tissue neoplasms that originate in the nervous system, which may arise anywhere in the body. However, GCTs are extremely uncommon in thyroid tumors, with a favorable prognosis. The diagnosis of GCTs is dependent on pathological and immunohistochemical analysis and at present, surgical resection is considered the only suitable treatment. Regular follow-up after surgery is an important way to monitor treatment outcome and recurrence. The present study describes a new pathological type of thyroid GCTs diagnosed by pathology and immunohistochemistry. A 14-year-old female was referred to the West China Hospital of Sichuan University (Chengdu, China), for thyroid incidentaloma. Laboratory examinations were within the normal range. Thyroid sonography demonstrated a solid hypoechoic mass in the right lobe of the thyroid. Fine needle aspiration cytology showed a suspicious malignant tumor and subsequently a total thyroidectomy was performed. Analysis of frozen sections, from obtained samples, did not facilitate a definite diagnosis. Finally, a thyroid benign granular tumor with atypical changes was diagnosed by postoperative pathology and immunohistochemistry. A 14-month post-operative follow-up showed that the patient experienced a stable recovery and had no signs of recurrence or metastasis. The case emphasizes that the diagnosis of thyroid granular cell tumors is predominantly based on postoperative morphology and immunophenotype. The clinical routine for the differential diagnosis may be due to: (i) neoplasms displaying a granular appearance mimicking granular cell tumors, or (ii) differential diagnosis in the pathological category of granular cell tumors. Further accumulation of such rare cases may be of clinical significance in aiding the diagnosis and treatment of GCTs.