Primary thyroid teratomas - A clinicopathologic study of 30 cases

BACKGROUND, Primary thyroid teratomas are rare thyroid gland neoplasms of g erm cell derivation that display features of trilineage differentiation. METHODS. The histologic and immunophenotypic features of 30 cases of thyroi d 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 year s (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 occ asionally infiltrative into the thyroid parenchyma. Derivatives of all thre e germ layers (ectoderm, mesoderm, and endoderm) were present in varying de grees of maturity. The tumors were divided into benign (n = 7 tumors), imma ture (n = 14 tumors), and malignant (n = 9 tumors) as determined by an incr easing percentage of tumor volume comprised of primitive mesenchymal or neu ral-type tissue. AU the microscopically malignant tumors occurred in the ad ult population. Surgical excision was performed in 28 patients, followed by adjuvant therapy in 5 patients. Follow-up was obtained in 26 patients; 8 p atients 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 a live 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 compon ent. The outcome is dependent largely on the age of the patient, the size o f the tumor at the time of initial presentation, and the presence and propo rtion of immaturity. Surgical excision is the treatment of choice, with adj uvant therapy reserved for the malignant cases. (C) 2000 American Cancer So ciety.