Malignant teratoma of the thyroid with predominantly neuroepithelial differentiation. Fine needle aspiration cytologic, histologic and immunocytochemical features of a case

BACKGROUND: Teratoma of the thyroid in adults is extremely rare, and most are malignant. Only nine cases have been adequately documented in the English-language literature, and there are no reports detailing the fine needle aspiration (FNA) cytologic characteristics. CASE: A 32-year-old female presented with a left-sided nodular thyroid mass with left cervical lymphadenopathy. FNA cytology of the thyroid and lymph nodes was done. The cytologic and immunocytochemical features were that of a small round cell tumor with neuroepithelial (NE) differentiation, metastasizing to the cervical nodes. Microscopic study of the thyroidectomy specimen showed a tumor showing an NE pattern with occasional islands of squamous and cuboidal epithelium, leading to a diagnosis of malignant teratoma. CONCLUSION: Knowledge of FNA cytologic features of rare but highly malignant lesions like thyroid teratomas allow early recognition so that suitable and possibly aggressive treatment protocols can be adopted in the hope of prolonging survival.