Primary thyroid teratoma in adults: A case report and systematic review of the literature

Extragonadal germ cell tumors are uncommon in adults and only 2-5% of teratomas develop in extragonadal sites. Primary thyroid teratomas represent <0.1% of all primary thyroid gland neoplasms. In the present report, a case of primary thyroid teratoma in a 6.5-year-old female is described. Furthermore, the current literature regarding patients who were diagnosed with primary thyroid teratoma and underwent surgical resection was systematically reviewed. A total of 15 studies of 27 patients (age range, 17-65 years). Growing mass or neck swelling were the primary symptoms in 14 patients (51.8%). Only one (5.5%) patient was preoperatively diagnosed with malignant thyroid teratoma. All patients underwent thyroidectomy, but 6 cases had more advanced surgery, including lymph node dissection. A total of 12 patients received a combination of adjuvant chemoradiation postoperatively, 10 (45.4%) patients reported recurrence of disease and 8 (29.6%) were postoperatively diagnosed with distant metastases. A total of 9 (39.1%) patients died due to progression of the disease. In conclusion, primary thyroid teratomas are rare and difficult to diagnose preoperatively. In particular, malignant cases are very aggressive tumors with a considerably poor prognosis, even after surgical resection combined with adjuvant chemoradiation.