Primary thyroid teratomas: a clinicopathologic study of 30 cases.

BACKGROUND: Primary thyroid teratomas are rare thyroid gland neoplasms of germ cell derivation that display features of trilineage differentiation.
METHODS: The histologic and immunophenotypic features of 30 cases of thyroid teratomas were reviewed, patient follow-up was obtained, and the results were analyzed statistically.
RESULTS: The patients included 15 females and 15 males ages newborn-56 years (mean, 12.4 years). All patients presented clinically with a mass in the thyroid, ranging in size from 2.0-13 cm in greatest dimension (mean, 6.0 cm). Histologically, the tumors usually were well circumscribed, although occasionally infiltrative into the thyroid parenchyma. Derivatives of all three germ layers (ectoderm, mesoderm, and endoderm) were present in varying degrees of maturity. The tumors were divided into benign (n = 7 tumors), immature (n = 14 tumors), and malignant (n = 9 tumors) as determined by an increasing percentage of tumor volume comprised of primitive mesenchymal or neural-type tissue. All the microscopically malignant tumors occurred in the adult population. Surgical excision was performed in 28 patients, followed by adjuvant therapy in 5 patients. Follow-up was obtained in 26 patients; 8 patients had died from or with tumor (5 neonates with immature histology and 3 adults with malignant histology; mean, 0.6 years) and 18 patients were alive with no evidence of disease at a mean of 16.9 years of follow-up.
CONCLUSIONS: Thyroid teratomas are rare neoplasms that can be divided into three types depending on the presence and proportion of the immature component. The outcome is dependent largely on the age of the patient, the size of the tumor at the time of initial presentation, and the presence and proportion of immaturity. Surgical excision is the treatment of choice, with adjuvant therapy reserved for the malignant cases. Copyright 2000 American Cancer Society.